Hi @Amy2884 Sounds like a challenging situation for both you and the guest. Scams happen, but it is difficult to discern if this might be one. If the guest is well reviewed with previous stays, then it is likely just an unfortunate event.
I would suggest a couple things as follows.:
1. Call Airbnb support and make them aware of the situation if you have not already. While customer service isn't always the best at navigating issues, they will document the case and can make suggestions if it reaches a point that the guest is not able to return. They may opt to open a case immediately or they may wait till he exceeds his check out time.
2. Make sure all communication with the guest is taking place via the platform. This way all conversations about him granting you permission to move and store his items is documented. In the event any issues arise later on, this will help support your side of events.
3. If A guest exceeds the agreed upon time of their stay, they are essentially no longer a guest, unless in the rare event they qualify for tenant or squatter rights which are typically reserved for stays over 30 days. It doesn't sound like the stay was an extended one.
I would make sure the guest's consent to pack their belongs is verbalized on the platform, pack their items, and notify them that you will securely store them for XXX amount of time. Let the guest know how they can arrange for pickup since you have new guests coming in and do not want to create a disturbance.
I am going to link another thread that has some similarities that might be helpful for you.
Guest won't check out, What are my rights? - Airbnb Community (withairbnb.com)