Here are some problems with that:
- Did you pay with a credit/debit card? If so, that shit's logged.
- Did you modify your appearance to foil the likely Internet-connected security camera watching the cashier? If not, evidence of your purchase is available there.
- Did you take the car you normally use to the store? If not, it's possible parking lot security cameras have identifying information on you, including a license plate number.
- Cell phone towers are at least capable of logging the towers and RSSI of MS's (i.e. cell phones) that communicate with them. It's possible if you've activated more than a couple phones that a pattern of movement, the correlation which could identify you, could be established against multiple IMSI's such as IMEI, ESN, etc. Especially if you use it a lot in single location like your house.
- Certainly the cell phone companies keep logs of the numbers dialed from a particular device. It's possible if you are statistically similar to previous units it can be said that your current phone matches usage patterns and can identify you.
- Sales records may indicate that an unusually large number of $15 cell phones have been bought at one location, revealing someone is trying to hide something.