Airbnb won't let you double-dip. If the guest left early, your cancellation policy kicks in, which in your case is Strict. That means If the guest arrives and decides to leave early, the nights not spent are not refunded. You cannot collect monies for nights you are ALREADY collecting money. Sit back and enjoy the free money while no one is staying with you.
Putting a note in your heading won't really help because if someone is looking for a night when you are already "booked", your listing won't be returned in the search results.