Madison police say the 19-year-old found a buyer willing to pay $700 for the laptop. They agreed to meet Tuesday about 10:45 p.m. in a grocery store parking lot.
The teen was explaining the nuances of the laptop but says the buyer seemed uninterested.
The buyer paid with a stack of $20 bills. When the teen returned home she realized the bills were counterfeit, with smeared ink and crooked print.
Authorities suggest Craigslist buyers and sellers meet in daylight hours in well-trafficked areas, such as a mall or even a police station lobby.