Are you saying that the entire port came off, that the one pin came loose, or that the cable came off the port (socket)?
If the entire socket/port came off of the board, you'll have a hard time getting it to properly seat with all of the connections in place, without resoldering it. I bet this isn't the case though.
The cable that goes into that socket is held firmly in place by pressure from the cover. The real problem is probably in the pins in the microUSB jack or in the actual battery connection from the jack. That isn't the battery connection I dont' think.