How to deal with horrible Sitters

So we had our first Sitters stay with our cat for a month. We came back today and...well. The cat seems to be doing alright. Our house not so much. It was incredible dirty, the toilet hasn't been cleaned at all, the whole bathroom reeks. Our shower is dirty and sticky and the drain doesn't work. The whole house stinks incredible - additionaly they used some kind of incensce (the told us in a handwritten letter they left) even though we told them not to use something like that, because our cat doesn't like that.

These are...well, it's bad for our cat but otherwise it seems they have taken care of him. We can clean the house... it's disgusting, but I guess we can't force them back to clean. What we can't fix is that they broke so much stuff.

There are several burn holes in our carpet. Our couch has a huge stain on it which they tried to clean (they say so in their letter with a sad smiley, because trying to clean it made it worse). its...ruined. They broke our shower handle. They broke a bike we borrowed them, so they can explore the surroundings (they say they fell of it, while riding it and couldn't fix it - in their letter). They used up important medicine from my gf, without asking and used our shampoos. They also seem to have used up my medicinal THC. We also have a beamer that seems to be broken...

I guess you get it, I don't have to tell you every detail. Well, we immediatly wrote Trusted Housesitter and they told us that we can only get the Home insurance from them, if our insurance denied a claim...so, we have to make a claim now and our insurance will become more expensive because these horrible people ruined our stuff? I know we are to blame, I didn't look into the terms of the Trusted Housesitter Insurance because we never thought something like this would happen...well. They had good reviews and seemed very nice and were..okay reliable with keeping us updated. Guess we know now..

Does anyone have any advice how we proceed? We never made any insurance claims, ever, so we really don't know what to do now and if Trusted Housesitter seriously won't help us.