That is a wonderful question! Ha! No idea! Honestly, this is what happens when stupid people are around and have to mess up a good thing.
I would like to "try" something...a good test would be if someone has entered their data into the spreadsheet (via the form) technically they should be able to edit their responses by going to the Form Link.
Can someone try this? If you are one of the early adopters, I think the best thing to do is enter your data into the spreadsheet through the form and in the Comments section write "early user" or something clever. I will then go into the sheet and delete your original line item.
Sound good!? Let me know.