I have had no success causing this to happen again. I just asked him for the exact steps taken to cause it and he showed me. He click on the Search Dx (ICD-9) button in the Diagnoses field. Then he typed the ICD-9 of the code he wanted into the ICD CODE field, clicked on the code when it came up, and clicked the Add Dx to Chart button. He wanted to move the code to a different portion of the Assessment field, so he selected the diagnosis (including the #, the ICD-9 code, and the

and used Ctrl+X to cut the text. Then he clicked on the line he wanted it placed in the Assessment field and used Ctrl+V to paste it in. When he did that the CC, HPI, RoS, and Assessment fields became blank.
As I said, I have had no luck re-enacting this and getting the same result. I spoke to him and told him about Ctrl+Z. Thanks, Martin! I use this shortcut in many programs but had never thought about it working in AC.
I checked the LastNoteBackUp.txt and the info was gone there too. What he was hoping for, and perhaps it would be better suited for the Wish List, was a better way to undo changes. The way I imagine the perfect undo button would be to have each iteration of a charts progress available in a menu, like Photoshop has. It is probably not something they would implement because it would almost never be used, but when you see one of those hour long patients with a giant history and so many other things that you have taken down and you lose your note because you hit the wrong key or the program had a glitch it could be very frustrating.