Cancellation within underwriting period, Virginia

I think I messed up. Asking whether there is any avenue for getting any help with this situation.

I bought a house in Blackstone, VA. The previous owners had let things go a bit, but had been living there. I got insurance immediately, paid for the whole year, and have been doing a bunch of fixing things up since I moved in.

I hired a local contractor to do some painting and some work in the kitchen, but we parted ways a couple of weeks ago because he was behind on every schedule he'd given me, and the painting he had done was very poor – loads of paint splashed where it shouldn't go. As we were parting ways, not on very agreeable terms, I saw him pulling away from my house in his pickup truck as I was getting back. Never saw him again. Was glad to be done with him.

Now, we've just had the first rain since, and I find my roof has been vandalized. Leaks everywhere, made deliberately with tools, need a new roof worth $13k. The damage is not visible from the ground.

And going through the mail, I found a letter from my insurer that I didn't look at from 3 weeks ago, cancelling the insurance effective 15 days after because of trees and bushes too near to the house. I just didn't look at the letter before. The trees and bushes are long gone, I had cleared them before the date on the letter.

Is there anything I can do? Should they have given me more notice, or notified me any other way? Do I have any kind of case, in that I'm sure the damage was done before the cancellation date stated in the letter, even though I only found out about it when it next rained? Or am I just screwed? I thought I was insured and can't afford a new roof.