Did you notice if the WTMD going off for other screenees at an unusually high rate, too? My experience has been that some airports have set their sensitivity way too high sometimes; I had one where it was the grommets on my hat that set it off (a few small grommets on a Panama Jack hat).

This was when they let you walk through with your hat (long ago), and some airports had theirs desensitized to the point I could walk through with my pocket knife, keys, etc. and not set them off, yet DAB had theirs so sensitive that taking my hat off and going through again was enough to pass.