Airbnb is not always great @Amy1772 but in a situation like this it's almost certain they would have helped you cancel the booking as it was clearly a third party booking. Please don't be put off contacting Airbnb in these situations because you have some people on forums who aren't treated well. Remember millions use Airbnb every day and have successful experiences.
If you have a local guest asking to stay it's also worth a bit exploration if they say some generic like 'weekend with my BF' unless it's a very young guest, most hosts would see a local wanting to stay for a weekend as a red flag for guests wanting to party or a third party booking.
Good for you for posting an honest review. Many hosts only accept guests after checking previous reviews - I know I do.
CCTV is a security camera, the idea is that you use it when guests check in to see that the person who books is the one checking in and that only the number of guests booked are using your property. You can also look to make sure they check out by your check out time.