Question regarding camo/invisibility

Is there a way for opponents to cheat and be able to see you if you have a camo/invis on? Perhaps turning up/down brightness?

Twice now, I've had a Prophet's Bane and had opponents actively seek me out and be able find me despite me crouching and not moving at all, completely invisible, just waiting for someone to walk by me. Once, I was shot by a guy with a railgun. And the other time I was spotted by a ghost, I somehow snuck away and he found me again a few seconds later.

I know when someone has an invis by me, I can't see them AT ALL. So I am truly baffled how they are able to see me.

Thanks.