Did you receive an e-mail confirming the booking? You have hosted quite a few guests so I'm sure you are aware of the message I refer to - check you inbox in particular hosting messages for this e-mail as that's one evidence.
Check you reservations as well; change default view to 'View all Reservations'
If you still can't find it then I suggest you contact Airbnb directly, click on the link for preferred contact option - Contact Airbnb