Landlord Claiming Cashier's Check Bounced but the Money Is Gone

Location: UT

My mom moved into an apartment and paid her move in fees with a cashier's check. The funds are gone from her account. The landlord is claiming that the check bounced and that she still owes the money. My mom has contacted her bank and they've said that they don't see any problems on their end.

I don't know what to do here. There was money in the account and now it's gone.

I find it hard to believe that this is some sort of scam because the apartment is owned by a large asset management company, it's not just some guy renting the place out. My guess is a mistake happened or something, but I understand it's possible that it's a scam.

Anyways, what do I do?