Originally Posted by
MSPeconomist
I'm guessing it was Russia; SVO is SU's hub, which is a SkyTeam member.
A further clue is that the OP didn't need a schengen visa, but would have needed a visa to leave the airport at the transit point. This would be consistent with, for example, a USA passport. I don't know whether the same would be true for a Singapore passport.
Well if it was SVO that certainly explains why the airline agents were particularly unhelpful.