It worked!!

I was skeptical of this tool at first, but it worked and saved my lost files back!! I keep my files in a Dropbox folder and sync with multiple PCs.
I mistakenly thought the files were safe as they exist at multiple locations in case they were lost, but I was WRONG. Dropbox is not a backup tool, it is a sync tool. When one file is deleted from one location, it will be deleted from other locations as well. When I found my important files were gone (I still do not know why this happened) from one of the folders in the Dropbox folder, I was very shocked and almost gave up restoring the lost files.
Luckily I found this Disk Drill, and it really worked and brought my lost files back. Thanks a lot!

Kuni O. about Disk Drill Media Recovery, v2.6.447