Withdrawn Consent

You're walking down the street and a police car drives past you, pulls into the next street and parks. The officer gets out and as you walk past him he asks you if you "have a moment to speak with" him. You stop to be polite and the officer informs you that he has been sent to a complaint involving a white male wearing blue jeans, a black coat and a Yankees cap who was carrying a backpack.

You happen to be a white male in blue jeans, a black coat, on your way home from work with a backpack, and you're also a Yankees fan. The officer explains that the person was reported to have stolen a GPS unit out of a parked car, and asks if you have one in your bag. You don't and when he asks to "check to make sure for his report" you give him the go-ahead.

So the officer starts searching your bag, and searching, and searching... and searching. You thought it would take a minute at the most to look through your bag, but this guy is looking at EVERYTHING.

After 5 minutes of him digging around, you tell him "this is taking too long, are you done yet?" and he replies that it's going to be another minute.

5 minutes later, he's still looking and you tell him "I'm going to be late getting home" just before he finds a small bag of marijuana in a small zippered pocket of the backpack.

Should he have stopped when you said it was taking too long? Should you have been more insistent? Once consent to search is given, how clear do you have to be if you want the search to stop?

Should you have to be a lawyer to figure out the proper phrase to stop the search, or should he stop the moment you express any thoughts about it? Did he exceed the scope of your consent?