One possibility here is that somehow the manager found out that one or more employees had agreed to go out with guest(s). Manager asked employee(s) about it. Said employee(s) CYA'd by saying the guest made unwanted advances and they never planned to follow through on the invitation.

In any case, this can of worms needs to be fed to the fish in the lobby aquarium.

At my employer with my boss, I would be informing said boss that the hotel manager had told me that front desk personnel accused me of making unwanted advances. I'd want her to learn that from me, not from any other source. YBMV (Your Boss May Vary).