So did the cleaner confess to taking the cash? Does the cleaner have a prior criminal record? What was missed in screening the employee?
Unless the cleaner confessed to stealing the cash it may be hard to prove that the cleaner took it. In the past few years I have found two wallets that were tossed -- neither had cash but had ID and cards. Had I been dishonest I could have tried to use the cards -- even though I did not take the cash. I returned both wallets -- one by mail and one by dropping off as it was nearby (left with doorman). Both apparently had cash in wallet; I received thank you notes from both owners - and both had cancelled the cards but were relieved to get ID and photos back.
It is disappointing that the wallet was not turned in intact, but the fault was leaving it in the first place.
Proving loss of cash is always difficult.