Stashed in the woods, on the ground. Often with a note which says something like.
"If you find this bike, it is not an abandoned bike. I'm hiking and depend on it to get home. Thanks."
My thinking is that if it IS found by someone wandering around, chances are good that it will be found by an honest person who went offtrail to relieve himself, or something like that. The sign is just in case he thinks that it is a stolen and abandoned bike.
I have left notes similiar on coolers filled with water/sport drinks/fruit for long mt bike rides.