ichidan verb, transitive verb
forget to look; fail to notice; overlook
Used when you forget to look at something, miss seeing it, or fail to recognize something you should have noticed. Often implies a lapse in attention or memory.
大事なメールを見忘れて、返信が遅れた。
I forgot to look at an important email and replied late.
To fail to recognize his face, you must have been really tired.