Thats the problem, the daughterboard with the mouse port is missing.
Then the daughterboard must have been snapped off, since it's completely attached to the board. On other revisions however, the mouseport is just a little flatcable with a 9-pins connector, just like in this picture:
http://www.amiga-hardware.com/download_photos/a1200mb_rev1d4.jpgIf you are just a very little bit handy, it's easy to make one yourself. Just rip apart a standard (IDE) flatcable and a serial port from an old pc and do some soldering. There's not much that can go wrong there if you have the pinout correct.
