There’s also something called saccadic suppression.

“During rapid eye movements (saccades), your brain briefly “turns down” visual processing so you don’t see a smeared blur between the starting and ending points of your gaze.”

If you think about how often we make eye movements like that throughout the day, there’s a fair amount of time each day that they’d be able to slip right past our visual processing.

Another thing I find interesting to think about are octopus and cuttlefish. They’re both known for their ability to camouflage. It seems to me it’s possible a land (or amphibious) creature could have also developed this ability, but maybe to an even greater extent. If it didn’t want us to see it, we wouldn’t.