Used A Spare Key To Take My Cats Back From My Ex’s Apartment

USA, Missouri. My ex and I broke up last year. He kept our cats for a while until my place was suitable for me to host them. When I was ready for the cats, he texted me to say he was taking back the spare key he had left for me to go visit the cats at his apartment, and that I would never see them again. The next day while he was at work, I went to his apartment and found a spare key I had hidden when I lived there and he had forgotten about. I took the cats in their carriers, nothing else, and locked the door behind me.

The cat adoption papers and vet bills are all in my name. They have always been mine. Now my ex keeps texting me saying the police want to talk to me because he reported that I burglarized his apartment and stole the cats from him.

What trouble could I be in?