Only UC admissions can give an official answer, but my feeling is you’ll be fine. From what I’ve read a “forgotten” class becomes an issue is when UC finds it during the summer when they use the National Student Clearinghouse and UC contacts you to find out what you took and to get an official transcript.
Since you’ve already notified them you don’t seem to be concealing anything. When you accept a UC offer be sure to send them an official transcript from this college.