Blimey, I’ve obviously touched a nerve. Maybe
My point was simply that the OP didn’t give any of the information. She doesn’t even say if there was a party at all, what kind of party it might have been, or what time her husband went to the gym, or whether he did anything else that day. She just said it was the baby’s first birthday. You’re making one hell of a leap here.
As I said in my post - if he needed to be around for a party (by which I meant the party and any associated ‘prep’) he should have been. The rest of the day, though, doesn’t matter.
I wouldn’t have a party for a one-year-old at all, personally. Not my scene. I might invite their grandparents over for cake and candles and take some photos, which is what my family and friends have mostly done. But that’s all. None of my mates have done the whole cake-smash photoshoot, balloon arch, mound of presents and catering kind of thing for first birthdays. So I didn’t make any assumptions either way about what was happening at the OP’s house.