I have had this happen. Almost the SAME exact thing.
But the thing is, I don't hang my hat on the timing of it all. Meaning, I KNOW how it usually goes when my Husband goes to a friend's to help fix something. I KNOW... it will be later than he said, and that THEN he and his friend WILL go have dinner. Because his friend will want to "thank" him for helping him, by getting him dinner.
That is just how it goes. *I* know that. I know my Husband.
In these situations, I don't cook "for" him according to when he THINKS he might be done and home. I cook, for me and my kids. IF he is home in time for dinner, fine. He can heat up the leftovers himself and eat. AND if he had already eaten dinner with his friend, fine. No biggie because I did not cook ONLY for him. I cook anyway, for me and my kids regardless if he is home or not, in time, for dinner.
For me personally, I know how long these things can take. Fixing the computer etc. then they hang out or whatever. Fine. I don't care when/if my Husband is home in time for "dinner" time, because that depends on WHEN I, cook or finish dinner. Not on when he comes home. I cook, when I cook, and the timing of that varies. Whether or not he is home.
Anyway, when my Husband has had spur of the moment things like that after work too, I don't ask him to tell me EXACTLY when he will be home, for dinner or not. I just keep doing whatever me and the kids are doing and eat, when WE eat and per when I finish cooking. I don't time it, according to when my Husband will be home from his friend's.
Because, I know, that my Husband is not good at timing things, like I am. And if he goes and eats dinner with his friend, no biggie. It really does not bug me at all.
I KNOW DARN WELL, my Husband typically runs late. Especially if he is at a friend's house fixing the computer.
So what.
I go about my evening, as I feel like it.
Sure my Husband will call me to let me know how its going. But I KNOW, he usually runs late. And he and his friend tends to waste time along the way just hanging out. So what. And if he eats dinner with his friend, so what.
Unless WE have another commitment on that same night, and my Husband is late... THEN, I would get irked and pissed. Because then, I would expect him to be ON time.