I guess it differs by geography, but here in Sweden, when I accidentally transferred €10k to an old account that didn't exist anymore I wasn't the least bit concerned that the money would get lost. I would have been extremely surprised if they hadn't given me the money back.

That's the advantage of a high trust society. Heck, once an ATM retracted my cash because I wasn't quick enough, I called the bank and they just credited my account with the €300 or whatever it was. No questions asked.