There is no way to recover a deleted form. TurboTax has no undo or backout.
You didn't say whether you are using TurboTax Online or the CD/Download TurboTax software. If you are using the CD/Download software you can use Save As to save the return with a different name. Then you can open the original return and it will be as it was when you last saved it. Depending on when you created the K-1 worksheet and when you last saved, that might allow you to recover the worksheet. But anything you entered since the last save will be only in the copy that you saved with a different name. There is no way to combine the two files or copy a form from one file to the other.
