Inconsistency in my man.....aaarrrggh!?

You said you made 'semi' plans...that implies that nothing was firm or set...something like "I'll catch up with you tomorrow" sounds like a 'semi' plan. If that's the case then him going to visit a friend who's son has an illness is fine as he didn't break any plans with you. In this case he doesn't owe you an apology. If you had firm plans, ie...i'll pick you up at 8:00 tomorrow and he skipped out then yes he should say he's sorry that something very important came up...