When moving a file to another volume, where does the original go?
The file is deleted on the spot. Which means technically it's still on the disk as a deleted file until the system overrides it. But with a running operating system, it's very unlikely you'd be able to get it back with a data recovery tool. Data Rescue does deleted file recovery, but the data you seek is most likely already overwritten.

It's also clear that the "missing" data was lost long before you moved it. Time Machine is your solution here. Keep going back until you can find a copy that is not missing the data.