Long term boyfriend didn’t get plus one

Hi everyone. My boyfriend and I have been dating for over 3 years and living together. He was recently invited to one of his friends weddings and told he would be a groomsman in the wedding. This wedding is also 10 hours away from where we live. We recently received the rsvp letter and he did not get a plus one. I was a little offended by this considering the large amount of money he is having to put into this for travel and groomsman things and not even able to bring me… he doesn’t know anyone else going to the wedding and is dreading it now. He is old college roommates with the groom and they have managed to keep up over the years. I have never met the couple since they are now states away from each other. We’ve talked a little over FaceTime here and there but nothing major. I know weddings get very complicated. I totally understand not wanting strangers/people you’ve never met at your wedding, but I just feel weird about it. I’m not sure if I’m being dramatic about the whole situation so I’m looking for some insight.

Edit to update: Thanks everybody for all the feedback! After realizing that this wasn’t a small wedding at all (7 groomsmen) and reading through this thread, my boyfriend decided to ask the groom. I was added to the guest list without question. We’ll never really know if it was intentional or not but the confrontation cleared this up and I will be attending now.