I don't think that they so much were looking AT me than trying to determine whether I was looking at them.

That would be hard to determine since I rarely give away what I'm looking at. I have become adept at looking sideways through dark glasses while keeping the head forward.

But, in all fairness, other then generalizations, being myopic, I can't see faces clearly without my glasses. Body shapes, types, yes. But, details, no way.