A bit miffed

So I've been away all this week due to work and my boyfriend and I agreed to meet on Friday after he has been to this event related to Uni. He asked me if I wanted to come along but I couldn't make it so he took his friend with him instead, which I was fine with. But he now says that he is going to be staying out till after teatime, because he wants to hang out with his friend after the Uni event, so this would be too late to meet. I don't have a problem with him staying out or meeting his friends of course but I've been away all week and we agreed to meet Friday yet now he has changed the plans last minute. Also, i got back from my work trip at around 3pm on Thursday and he got home from meeting his dad at around 2 yet made no attempt to want to meet up. He has been with his friends all week, which is completely fine, so I'm a bit miffed that he is spending the day we were supposed to meet up with his friends. We have been together for a few years and I trust him completely in terms of loyalty, but am I right to be feeling a bit miffed at his changing of our plans? I've tried to explain how I feel but he doesn't think I should be annoyed about this