When someone accidentally sent me 200 EUR about 15 years ago it sure as heck didn’t stay mine: their bank contacted mine, which then contacted me to warn me that they would soon be pulling it back out. The sender had transposed numbers in the Bankleitzahl - the pre-SEPA number codes for German banks that are still in modern IBANs, and I happened to have the same account number as someone at that other bank (all little community Sparkassen). Those Bankleitzahlen didn’t have any sort of checksum digits, but IBANs do, preventing most of these kinds of accidents.