The theft happened at the Wawa store at 342 Third Avenue on Friday around 2:15 p.m.
According to investigators, the woman came into the store a few minutes beforehand, picked up the jar, but then put it down.
She came back later to buy cigarettes and candy. As she left the store with her purchases, police say she also left with the collection jar.
The money inside was to be used to help the Fielder family, whose home in Petersburg was heavily damaged in an October 5th fire.
One of the family members, Thomas Fielder, had previously worked at that Wawa store, and his former co-workers were raising money to help.
Anyone with information is asked to contact Stone Harbor Police at 609-368-2111 Ext 132.