I'm amazed that you asked the question if your husband has 15 years as an insurance adjuster. (I'm not an adjuster. I'm an investigator)
Your argument (obviously) is that the damage was willful, not accidental, and the mother is, therefore, responsible.
You had already filed in Small Claims when you asked this?
I must have misread it - I took it as a "who is right" moral question instead of a legal question. I think the answers are different - but the check already was returned to her so that option is moot.