Duplicate of The specified item was not found. -- please reply there.
Use the History panel. You can go back to any editing step. You can also save snapshots at any point.
Your Library may get a bit cluttered if you create VC's for every edit. I use VC's for example to make an image with a different crop aspect ratio to the original where I need to keep both copies for exporting to different projects.
From the Develop module, look at your History panel on the left. As you click on each entry, the main display will update to what that state was. If you make an edit while in the middle of the history list, all the newer (top) entries will be discarded and your new edits will take over.
You can create virtual copies if you want, but it is not necessary.
You can also create virtual copies from any point in the edit history including the beginning, at any time.
The "reset" button will discard all of the edit history for the current image.
You can also just click on the "imported" entry at the bottom of the edit history and start editing again from there.
but if I go back several days later and change my mind, I can't...
Your previous editing steps will still be in the History panel, so you can go back and change anything anytime.
There is no need to work on a virtual copy unless you want to compare two different inrterpretations of the raw file.