Is there a claim my ex husband deposited a check in both our names without my signature

While my husband and I were still married, we had a windshield repaired. our divorce became final. afterwards insurance sent insurance claim check to me at my address in PA. My ex has since moved to NY state. We are not on speaking terms so, I sent him that check, unsigned, in haste. Sent him a text and told him to return it to me and I would sign it and return it to him. He didn't. I called Insurance company. They confirmed this check was in fact deposited into his Credit Union account as deposit only without my signature. Is this legal? What are my rights? Prior to me sending the check to him, I checked with my Credit Union here in PA and was informed I needed both signatures to be able to deposit that check. Why was he able to deposit that check without my signature and not I?