Yikes! That's crazy. Glad you found it.
I've actually done this several times. Years ago I used to keep my release in a top pouch. I was late one morning, parked, quickly slung my backpack, grabbed my bow and high tailed it to the tree. As I was setting up I couldn't find my release. I didn't carry a backup at that time. I knew the last place I saw it was when I was getting ready at the truck so I snuck back to the truck. It was sitting right there on the ground by my drivers door. I must not have zipped the pouch all the way closed. Rushing leads to mistakes. I finished out the hunt and swore from now on I would have a back up release and attach my release to my bow so I know where it is and I could visually inspect that I have it before leaving the truck. Now fast forward to this year. I got set up one morning and no release on my bow. I remember doing putting it on the day before. However I was rushing to get out of there to get to my Grandson's B-Day party. Rushing leads to mistakes. When will I ever learn? Anyway I pulled out my back up and finished my hunt. Great hunt! I saw lot's of deer, learned a new area and saw a buck fight between 2 shooters 50 yds away. On the way back to the truck, I searched the river bank for my release and didn't see it. The most likely place that I could have lost it was along the river so I kept looking every time through. The 3rd time through, there it was laying in about 2" of water. I cleaned and lubed it and she's was as good as new. In my haste, I put the buckle pin through the 1st hole and only had a small tag end through the buckle. Normally I get it as tight as it will around my bow and have about 1" tag end hanging out. You live and you learn. Slow down! Rushing leads to mistakes.