I have a pocket on my life jacket, goes in there.

Shayne, check your owner's manual, most cars have one old-style keyhole hidden somewhere in case of a dead fob or car battery, mine is in the obvious place, but my wife's is actually hidden in the trim under the driver's side handle, It'll save you the cost of a window...

I recently replace a vehicle, and went from the "old fashioned key" to a key FOB.  I'm not really familiar with the technology so I never "stashed" my keys anywhere and wouldn't with the key fob either.  I brought both key fobs with me on my last canoe trip.  Home is 6 hours from the access point so leaving one at home as a backup didn't make sense.  Both FOBs were in waterproof pouches in different locations between my packs./canoe.
My vehicle also has the flip out metal tab to enter the vehicle should the FOB be DOA.  
 

Petey- "Every standard car we have ever had was bump started at one time or another...until we got a 2014 Ford Focus. Guessing that the engine management system was the culprit. With no power in the battery it kept it from starting when we rolled it down a hill after draining the battery. It also kills all power when it senses wheel spin. Dangerous when trying to get going on snowy roads."

that's actually nothing new, cars now have an interlock to prevent them from starting in gear to prevent a runaway, plus all automatic and some manual transmissions have mechanical pressure pumps to lubricate them that only work when the engine is running, ( hint- trannys using 75w or 85w90 gear oil don't have pumps) continually trying to bumpstart them wrecks the pump (turns it backwards) and eventually the transmission.
as for the wheel spin there's usually a button or switch somewhere to turn off "traction control", it's not actually killing power, it's using the ABS system to apply brakes to the spinning wheel, which in turn kills the momentum of the vehicle to "allow the spinning wheel to slow down to the vehicle speed " (owner's manual words, not mine) It can actually be annoying and dangerous at times, like entering a snowy highway, because it 1) prevents the tire from using momentum to clear snow from the tread (self- cleaning tread), and 2) because you're literally dragging one wheel, it can prevent you from getting enough speed to enter safely from a snowy ramp to a dry highway. 
I HATE TC and turn it off in poor weather because while it may be safer than some luddite who never learned to drive properly, it's actually more dangerous for people who DO know how to drive in bad weather and can control their wheel spin...
Warning to others with a locking rear end-I drive a 4x4 with a factory electronic locker in the back and TC has actually CAUSED me to spin because both back wheels will lock up if it detects spin, making them slide with no control whatsoever...

Dave; I never just " just stick the key in a zippered pants pocket", I've yet to find a fob that is truly waterproof, merely water- resistant, and tuck mine in a small, heavy-duty ziplock type pouch that came with some long forgotten electronics.
Years ago I forgot the pouch and just put the key in my pocket, and yup, I dumped...
that poor fob never worked again...

Scoutergriz - yeah, I am taking a bit of a chance there, all it takes is one quick kersploosh and thats that.  I pledge to be smarter about that next season.  Even a short paddle could result in a long walk home...

Shayne - sorry about your son's car.  You never know who is going to show up.  The worst I ever had is mice getting into the rav while I was on a 3 day trip in the adirondacks.  They didn't find any food stuff, which I foolishly left available, but they pooped all over the blasted car!  Turns out the rav has an open spot of entry where the cabin air intake is.  Addressed that and no mice since.

scoutergriz wrote:

Petey- "Every standard car we have ever had was bump started at one time or another...until we got a 2014 Ford Focus. Guessing that the engine management system was the culprit. With no power in the battery it kept it from starting when we rolled it down a hill after draining the battery. It also kills all power when it senses wheel spin. Dangerous when trying to get going on snowy roads."

that's actually nothing new, cars now have an interlock to prevent them from starting in gear to prevent a runaway, plus all automatic and some manual transmissions have mechanical pressure pumps to lubricate them that only work when the engine is running, ( hint- trannys using 75w or 85w90 gear oil don't have pumps) continually trying to bumpstart them wrecks the pump (turns it backwards) and eventually the transmission.
as for the wheel spin there's usually a button or switch somewhere to turn off "traction control", it's not actually killing power, it's using the ABS system to apply brakes to the spinning wheel, which in turn kills the momentum of the vehicle to "allow the spinning wheel to slow down to the vehicle speed " (owner's manual words, not mine) It can actually be annoying and dangerous at times, like entering a snowy highway, because it 1) prevents the tire from using momentum to clear snow from the tread (self- cleaning tread), and 2) because you're literally dragging one wheel, it can prevent you from getting enough speed to enter safely from a snowy ramp to a dry highway. 
I HATE TC and turn it off in poor weather because while it may be safer than some luddite who never learned to drive properly, it's actually more dangerous for people who DO know how to drive in bad weather and can control their wheel spin...
Warning to others with a locking rear end-I drive a 4x4 with a factory electronic locker in the back and TC has actually CAUSED me to spin because both back wheels will lock up if it detects spin, making them slide with no control whatsoever...

Some good info in that post. Thanks. My car didn't come with the TC off button. Thought about messing with the fuses to turn it off but not sure if it would cause other problems. Had to get the parking brake fixed recently as the car would roll down hill even though it was in gear and the brake applied. Works like a charm now that I got that repaired.
Two years ago I got a flat tire on the 401 and managed to wreck the wheel sensor at that corner. Caused braking and engine power problems. Was headed to Mew for a March camping trip. Had to limp home and rent a car to get to the park.
Try to always keep my keys in the PFD pocket getting back to the topic at hand.