That really depends on the MSC and I am not going to ask which MSC this was for as I think I know. If you look over the form, is there any place for 'unusual occurrences' or such? If so, I would mention the graciousness of the cashier in holding my groceries while I retrieved my wallet, which was accidentally dropped in my car.
I don't see it as being a disqualifier for the shop if you use it as an opportunity to praise a cashier going 'above and beyond'. If there is no such place to say something good about the cashier, I think I would just be silent assuming it did not impact your timings and I would use my first exit from the store rather than my second as the end time for the shop if it is after the time stamp on the receipt.