SMF handles groups  differently, and I think might even be slightly bugged, or I am not understanding something.

So for example, Tehill is on the devteam and is a mapmaster, but is listed as neither for some reason.

Both Grommit and Torchwood are mapmasters, devs, and vols (etc). But Grommit is listed as a vol only and Torch as a Mapmaster only. Why? No idea.

So don't put too much stock in the groups shown ATM.

But if some non-public group which you used to have access to (they're all in Administration) has disappeared, post here because something  is probably just set wrong.

OK, now that it's in the right place I will add him.