Bicycle detail

I rode the Baltimore bike party and we took a rest stop at Clifton Park in Baltimore city. I rode my red Specialized Rock hopper bike. It was originally a mountain bike but I changed the tires and put on road bike tires. I put the bike down and I sat down at a picnic table and put the bike about 2 feet in front of me. I had a conversation with someone at the picnic table and then people in the group said lets go and I turned to pick up my bike and it was gone. Other people had their bikes stolen as well. Some thug grabbed a young womans bike from her hands and pushed her to the ground other people at the bike party tackled the thief and she got her bike back. I went to the police station with another guy who had his new mountain bike stolen. It also had a red U lock around the frame and it was locked around the front of the frame but the wheels were not locked.