Thanks, @maglib, but I'm confident that I need to amend (I double-entered the income from a 1099, and didn't bother to look over a print version before I e-filed, so I saw my mistake just a few minutes too late. Let that be a lesson for you, kids.) And I followed exactly the process you described to produce the amended return. Like some others on this thread, I figured it was the fact that it was an amended return that triggered TT's "unable to locate attachment" error.
