I need to amend my 2012 return. I have the return and 2012 Turbo Tax software on my computer. However, the software says I didn't e-file my return so I can't amend it. I did file the return.

I tried switching to "print and mail" rather than e-file, to trick it, but it still gives me the same error. I don't want to have to re-input everything. How can I convince it that the return is complete?