crowd face
The kind of face that blends into a crowd. Someone you know might have a crowd face if you've met many times but can't seem to recognize them. Or if you can't pick them out of pictures.
"Dude, why didn't you talk to Sandy?"
"That was Sandy? I can't seem to recognize her, she must have a crowd face."
"That was Sandy? I can't seem to recognize her, she must have a crowd face."