This has happened to me before, too! It was a McDonald's drive-thru. I didn't get "reimbursed" for that portion of the shop as I did not have an outlay of money to be reimbursed for. I did the report, as this was a dine-in followed by the drive-thru; I did get reimbursed for my dine-in portion. I would agree with mjt9598 - you can't do it this time as you've already submitted the report, but reschedule if at all possible and get TWO meals - one free and the other in exchange for the report.
On a side note, I've twice done hotels shops where the cost of the room was reduced to zero by the hotel manager because of a bad experience (first one, key wouldn't let me back into the hotel in the middle of winter, middle of the night, and I had to walk the long way around in the freezing cold and snow to get back in the front door, and second, the clerk did not set up or explain how to use the hearing accessible kit that was just handed to me at check-in - a requirement of the shop). I did the reports for "free" (they were reimbursement only and there was nothing to be reimbursed) because of the rotation (I couldn't go back the next weekend as they would have remembered me) and I didn't want the black mark of being labeled a "flake" on my record. Besides, the hotel is interested in how bad experiences are handled. Would have been nice to have been paid something for my work, but I consoled myself with the thought that I didn't have to wait over a month for the reimbursement check from the MSC.