Tis Time to Smell the Roses - S7-E23
Other mistake: When Al talks about the man who bought the shoe store he wanted to buy, he says the same guy bought the store he used to work at and got his old job back. However, Gary is a woman who owned the store before this episode and again afterwards for the remaining episodes. So it couldn't have been bought by a man because Gary the woman still owns it.
Answer: It's implied that Steve filed for divorce since in s04e16, "You Gotta Know When to Hold 'Em", Marcy says that Steve is suing for alimony. Alimony is something that has to be requested when filing for divorce. Although the show doesn't spend time on the actual legal proceedings of their divorce.
Bishop73