You are driving home with a bag of takeout food. You're forced to make a hard stop and the bag flies onto the floor, expelling a single french fry onto the dirty passenger floor mat. In your panic to retreive the bag, the nasty fry somehow escapes back into the bag. You caught a maybe half-second glimpse of half of the fry.
Explain how you use your detective skills to detect and excise the offending fry when you get home