My job mailed me my last check and an exit interview but didn’t tell me I was fired or let go.

So I worked at this for about 11 months. It was toxic from day one and I went on call at my other job I’ve had for over nine years. I tried to put in my notice twice but they said they needed me and promised me a promotion which never came. So I finally had enough at the end of November and said I’d stay on call and they could call me if they needed me to fill in days. I returned to my other (old) job full time because I know I can manage the work for now until I figure out what I’m doing. I’m just wondering if this is legal to be let go without notice or a reason? I live in California if that makes any difference.