Form does not exist

I recently printed some leaflets with the QR code and URL to my forms and had 40+ responses. 

I had made some minor changes to the form and the outcome of the blue when you scan the form you get an error message that read "the form does now exist".... The thing is ,it does exist. It's not in the deleted bin it's active, it's just upon further exploration I can see the QR code and URL has changed. I have been using the tick box that says make URL shorter...could it be that? Does this change the URL and QR Code every time you press it?