@Celina136
Okay, this is an unfortunate situation, but there are a few things that might explain it...
Firstly, third party bookings are not technically allowed on Airbnb (and there are many good reasons for this). The guest booking must be one of the guests staying at the listing and, if you reserved the listing via Instant Booking, the host has every right to have it cancelled without penalty because it's against the rules. I have had to do this a number of times.
Now, if the instant booking falls outside of the period in which a guest is entitled to a refund, it gets more complicated. If the guest cancels in these circumstances, they will lose money. However, if the host cancels without the penalty free clause, the guest will be refunded and the host will be penalised.
So, it seems most likely to me that the host initiated a penalty free cancellation for themselves because your booking was against Airbnb ToS. Personally, I would not have done this. I would have contacted Airbnb and asked them to issue a penalty free cancellation with a refund to the guest, but I guess not all hosts are happy to do that at the last minute. Your host might have felt that your booking, even though it was not active for long, tied up their calendar during a particularly busy period and therefore lost them income. That is a bit doubtful though, as the dates should have been booked already. However, it's possible the dates were only freed up last minute due to another cancellation and would have gotten booked quickly if you had not made the booking.
Sorry if that sounds overly complicated, but what I am trying to say is there are several possible scenarios here and, although one of them could be that it's a scam, there are others where it might not have been a scam.