No gas analysis, no pass. Maybe you just didn't see them do it. Sometimes they'll stick the pipe in and carry on checking lights etc at the same time. As it's all done on a computer now, they can't skip the emmissions test.
The gas analysers are linked to the computer but you're right, not every car needs an emissions test (pre 70-somethings I think and LPG). But they do input your car's details into the computer before starting the test so I would have thought it would have come up with the requirement for gas test. Maybe someone more au fait with MOT tests can enlighten us?