Husband forgot to change his diaper 🙄

So I’m a stay at home mom and my husband works. He works like crazy and has a long commute. So I’m with my toddler more then he is, once my husband is home he obviously helps out ect, but he never really is with him alone, because I never go out and if I do it’s my moms house or I’ll take my son out in the day while my husband is at work. Weekends we like to go out as a family. My husband is always saying go out, you should do stuff by yourself, but never do so my husband isn’t really alone with our kid. Tonight I got invited to a girls party an my husband took our son to his friends, but forgot to change his diaper, we get home at the same time an I noticed my son is walking kinda funny and I asked my husband why he didn’t change his diaper, assuming he probably has a rash now, an so we take it off an I said see there’s a tiny rash an he’s like it’s one time I forgot, you can tell he felt so guilty but was a little defensive cuz I was making him feel bad. I ended up giving him a bath real quick and put cream on, he’s fine an walking normal, but any tips on how to remind my husband next time he watches him alone to change his diaper with out making him feel bad? I think he learned his lesson but still... I’m also very picky about how things are done so I feel don’t give him a chance.