I can think of other possible scenarios as to why Jessica left the store with the cash drawer open and her purse on the counter.
One possibility is that the suspect went into the station, approached the counter, flashed a weapon and forced Jessica to move away from the counter.
Another possibility is that the suspect went into the station, looked at the merchandise in an aisle, and then was seen going into the back room and Jessica left the counter to confront the person in the back room.
Cebee also pointed out the possibility that someone could have entered the station from an unlocked back door in the back room, and the noise from the back room caused Jessica to leave the counter to check the back room.
Something transpired inside the station that night. If someone didnt lure her away from the counter, then someone forced her away from the counter.