Okay, if you were so careful, then why do you carry it around with you instead put it in a locker or your back bag? Since it's always there and nobody going to take your back bag and find your wallet...
Doesn't matter if it was an accident, you're still dumbo for doing it anyway.
Left my wallet in a bus around a month ago, some lady took the wallet and gave it to driver so I called them and got my wallet back. Had 200 $ in the wallet because I just came back from Florida and around 2000 CZK (85 $), credit card, drivers license and all that. Not a single coin was missing.
Just always pat yourself down before you go anywhere, anytime I leave a place I know I had my phone or wallet at. Just pat down my pockets before I leave to make sure I have everything. Still sucks man sorry to hear about it.
I lost my wallet during a ride to bank so I can put the money on the bank account, a lady found in on the street and picked it up, I also posted a message on Facebook group asking if anyone has seen the wallet, but then my mum send me a sms saying that someone had found my wallet and they have it, they're on this preschool place, it had everything like it was left, even the five euros. And ever since then, I either have it in my deep back bocket jeans, or in my back bag.