@Coralia2
So sorry this happened to you.
It sounds like you had no communication with the host since you booked in October - not even to confirm check in (which is very unusual0 - so this must have come as such a shock to you.
At the very least the host should have sent you a sincere apology and explained what had gone wrong. They must have known what a difficult position this put you in.
And Airbnb should have helped you found an alternative and looked to extend the credit beyond their standard 10% as it was such a last minute cancellation at peak season. Sounds like you didn't get such great customer service.
As @Branka-and-Silvia0 says sometimes it is absolutely unavoidable that a last minute cancellation happens - there could have been a death in the family, a boiler broke down or some other malfunction which meant the listing couldn't be used.
Unfortunately there are a tiny element of hosts who don't behave responsibly and can double book or otherwise not have their place available. I wish Airnb and other listing companies would kick hosts like this off their platform.
Being frank last minute cancellations could happen with any accommodation you book whether with airbnb, tripadviser homeaway etc. Or even in hotels.