Oh, then how do you know it was him?
5 seconds sound clip from the The Incredibles (2004) movie soundboard.
You can hear this line at 00:13:52 in the Blu-ray version of the movie.
Quote context
[...]
- He says.
- He puts thumbtacks on my stool.
- Well... Not really. No. Actually, not.
- Oh, then how do you know it was him?
- I hid a camera. Yeah, and this time, I've got him.
- See? You see? You don't see it?
- He moves! Right there! Wait, wait! Right there!
[...]