FWIW, the CPU may not have done it. It will say AI in history if by the end of season there was no owner. If there was an owner say from week 2 to 15 mess up the cap, it will still show AI.
I'm not fond of what the AI does (or doesn't) but cut it some slack .. LOL
You can search the team name in league forums and it should give when an owner had picked up the team ..