Should I Be Upset?

So my bf and his friend went to Vegas over the spring break. I wanted to go with them but I'm 19 and they're 22 and 23 so I totally understand why they wouldn't want me to go. He said the break would even be good for us since we're hallmates so we see each other everyday so I was chillin. However, i ended up fininding out that my bf and his friend went with a mutual friend and she's 20. He didn't tell me until their last day being there. Should this bother me?