What happens when you get your id taken away at a bar (in Boston) & they say a detail cop is on his way?

I was using my sisters ID last night and the bouncer said it didn't look like me & took my ID even though I had all the back up and answered all the questions he asked correctly. It was the first bar we went to & I really wanted my ID back so I hung around the bouncer & kept asking when I was getting it back so he would start to rethink if it really was me. He pulled me aside and said that I need to admit it's not me or else the detail cop will come & deal with the situation. Obviously I didn't admit it wasn't me so the bouncer kind of just kept blowing me off and ignoring me when i asked when the cop was coming. Finally he had another bouncer come and look at the ID and after they talked in the corner he gave me my ID back and said not to come back. So the cop didn't even come. I was just wondering if they just say that the cop is coming as a way to scare you into leaving or if the cops really actually do come. I was there for about 45 minutes and no cops came. If the cops do actually come how will they be able to tell that it's not my ID? my sister and I look very similar...