Is it possible to recover files deleted by upgrade to v3?

I have a cruzer glide 32GB sandisk encrypted USB.  I recently was prompted to upgrade from v2 to v3. Unfortunately, I neglected to back up my files. When installation of v3 was completed, I could not read any of my files. I tried with one of the commercially available recovery softwares, but all I can recover are .htm and .pdf files concerning the modialities of the upgrade. Now I have uninstalled v3, and am back to v2; however, I still cannot know if my files still exist, or have been permanently erased. I am very naive technologically, but I would hope that the files are still there, but unreadable. Is there any way to recover these files?

I apologize if this question has already been asked; I am new to the forum.  Thank you for any help that may be offered.

Hello. I’m new to the forum as well. I don’t possess any particular expertise. However, I have had a slightly similar issue to yourself. You mention that you did not back up your files before upgrading. Can I ask if you have retained somewhere the encrypted form of your Version 2 files? These files would have been contained in the sandisk’s vault folder. If you have retained the encrypted files somewhere (eg on your hard drive or on a USB etc), it seems it is possible to restore them onto the version 2 again - I have just done that successfully. I think that if you haven’t kept a copy of your files in any form, then I would say that they have gone permanently. Again, I emphasise that I’m not an expert in this. Others may be able to give you more informed advice. Happy to discuss further.