Just because it wasn't unintentional doesn't mean it isn't still negligence. If you forget to unplug your lipo battery and it catches your place on fire, it's still kinda your fault since you plugged the battery in in the first place. I'm not here to beat anyone up. The OP needs a lawyer and with some hope, will come away without (at least) full responsibility.

I would recommend renters insurance in the future. It's cheap and *may* cover something like this.