TurboTax Online saves only the most recent version of your tax return. It does not retain previous versions. When you amended your return, the amended version was saved and replaced the original version. If you did not save a copy of the original version on your own computer before you amended it, there is no way to get the original version from TurboTax.
The instructions that Critter-3 gave you will let you reconstruct your original return in TurboTax, but it depends to a large extent on your knowledge of what you changed. Column B of the 1040-X will show you the changes in the total amounts, but not the specific changes that you made. The explanation of the changes that you provided in Part III of the 1040-X should help you remember what you changed.
Caution: Save a complete copy of your amended return before you start trying to undo it. Once you cancel the 1040-X, it will be gone, with no way to retrieve it. As I said above, TurboTax Online saves only the most recent version of your tax return. The reconstruction, or attempted reconstruction, of the original return will replace the amended return.
Your accountant, with your permission, can get a transcript of your original tax return from the IRS. This would be a lot easier than trying to reconstruct your original return yourself, and would eliminate the possibility of errors in the reconstruction.
