You are right about the grammar theory on the word "forget" but this partcular sentence is a different thing.Originally Posted by blacknomi
I think it should read:
Aren't you forgetting something?
It's a phrase one would use when you are giving the person a little hint and a nudge to see if they remember what it is they are forgetting.
ex. I am almost out the door when my sister stops me to say:
-Aren't you forgetting something?
-Oh, yeah, my driver's license, of course. Again!
Student or Learner