The store at the RAF's Cranwell base was shut for four hours during the scare, in which more than 200 people were evacuated from the area.
The bag was spotted in the confectionery aisle by two female members of staff and supervisor Bev Kishere informed the police. An RAF ambulance, Lincolnshire and RAF police, and the RAF fire brigade were also called to the scene as a precautionary measure. Roads were also closed.
An officer from the RAF bomb disposal team carried out the controlled explosion of the bag, which was discovered to contain a child's PE kit.
Bev told Convenience Store: "We're told to be aware of things like this because of our location. I treated it as suspicious and informed the police as it was the safest thing to do and because nobody had seen anyone drop it in the store.
"I didn't quite expect so much disruption, though. There was some minor damage to the tobacco gantry, but that's now been fixed.
"Everything's just about back to normal now."