Today I saw a gym that had been taken over by Team Mystic, which is my team. It only had 2 Pokemon in it. I placed my highest Pokemon on the gym, and about half an hour later I was looking at my phone and noticed it was being attacked. I figured it was going to be taken over by one of the other teams.
It turned grey and stayed that way for about 5 minutes which was odd. It then went right back to Blue with 3 Pokemon on it, except I wasn't the third Pokemon - I got kicked out!
Why did I get kicked out?