Why does my bf sometimes forget to call me when he's out?

We’ve been together almost 5 years and we’re currently long distance (a year and half now). We usually talk every night and say goodnight before we sleep…but I always hate when he goes out and he says he’ll call me to say good night but DOESN’T! I stay up waiting for hours because he’ll say he will call but then he doesn’t pick up his phone!

Last night he was at his female friend’s house with his brother and she was taking them home. He said he was gonna call and he never did and it made my imagination run wild the whole night. It really upset me, and he knows that when he forgets to call it makes me angry.

I mean all I wanted was to talk for a few minutes cuz I didn’t get to talk to him today :(