I have seen the eye call and tell the pit there was an overpayment on numerous occiations.
The pit makes the call on whether or not to ask for it back.
Regardless of the conversation you had with the dealer, they could and have asked for it back. I have seen customers refuse to give it back. Depending on who the customer is, I have seen them asked to leave. The dealer is always in trouble on an overpayment. Could be a writeup, could be his job.

There was a big stink with Pete Rose at the MGM awhile back. Dealer over paid him $5,000 on a bet. Rose refused to give it back. Not sure what happened to the dealer but I can not imagine she is still dealing for the MGM.

Small or large, the dealer is in trouble.