unfortunately, i think most of the time this one sided - and what, to you, seems like ' a moment', is probably just in your head.
if you are with someone, and you are looking into their eyes, they will likely look back at you and smile - unless you are being really weird and they are a bit freaked.
most people will be a little bit freaked if someones eyes are boring into theirs and look back and try to assess whats happening - so this could be misconstrued as a mutual feeling.
it can happen of course, but I have had a guy trying to smoulder at me and imply a kind of special bond - and i just felt creeped, but i reckon he thought there was something special there.
i have also felt a 'vibe' or 'chemistry' with someone, sure they felt it too, only to have them be completely uninterested.