@Nicole362
Why does the guest think the host has to check with Airbnb about a non-existent booking??? If the guest really did make a reservation and really did pay, then the booking and payment is entirely between Airbnb and the Guest. If the host has no reservation showing, then the host has nothing to ask about. If the guest does have a reservation then he can use that info to contact Airbnb.
Just calmly tell the guest you have no idea what he's talking about, and that HE should be the one to talk to Airbnb. Show him your "Upcoming reservations" page is you have to - but don't get involved. Any problem he has is between him and Airbnb. Be sympathetic, but make it very clear that it's not your (the host's) problem.