Is this strange or was it me?

My boyfriend went to a bachelor party on friday... I giess it's the rule to have "phone silence" for all the guys with girlfriends... Anyways I hadn't checked my comp. all weekend so I looked at his facebook page to see what the boys were up to... I saw something then noticed to my suprise what I wasn't even looking for a girl who wrote on there saying the day he got to the bachelor party weekend trip "I'll hit you up at about 2:30 am"... I thought it was strange so I called him and asked him who is this and on... He said he didn't know who it was he'll check it out.. He calls back and says "oh that was so and so's ex girlfriend and it was her birthday (whom he was friends with but they aren't talking right now because they got in a big fight).. Then he said ya I think it's weird to and got upset at me saying.. I'm still mad.. I don't know what to think... What do you think is going on??