Mr. Monk and the Red Herring - S3-E10
Revealing mistake: When Julie's teacher is searching the name 'Larry Tilburn', he isn't typing into a search engine, virtual encyclopedia, or anything of the type, the computer just shows a blue screen with a popup message in the middle.
Answer: Notice also that in the opening credits scene when he is touching parking meters her also wipes his hand on his clothes each time he does it.