The one thing I can think of is, that MF assigned it to you and to another shopper. The other shopper has already submitted the report.
I only say this because one time I had a demo and went online to enter it and there it was, already entered. I called my supervisor and she said someone else did the demo at the store. I told her no, they did not, they may have filled out the report but they were never in the store...(turns out the girl "said" she was there but she was "not" confirmed by the manager and she falsified a report to get paid).
It may be something different but it is possible a fluke caused you both to get the shop?