Do you need any help?
This happened to me a few weeks ago and I'm pretty proud of this line I made up.
I was walking around in a department store with this girl, and a worker came up to us and asked
"Do you guys need any help?"
I responded with the usual "No thanks" and then quickly added "I already found everything I'm looking for"
My friend gasped a little, and as I walked away, I heard the worker say "Damn that was good."