Maybe you see a plant you have to collect in game or a rock wall that looks different. What items have you caught out of the corner of your eye that you realized was just your brain so focused on looking for things in a game that you saw it IRL and made you double take?
I fell into PUBG pretty hard when it hit early access a few years ago. To the point that one day, whilst at work I saw something on the floor and off in the distance. For a breif second I mistook it for a Vector submachine gun.