Personal files now missing on Windows 10 bootable USB, after entering Advanced Start-up mode

[nivedr15]

I had a windows 10 bootable USB with extra personal files on it. I just tried to do an advanced start-up using the USB, but it failed. Now when I access the USB, only the windows 10 files show up and the personal files are not there. I have tried viewing the drive with hidden items checked, but to no avail.

I think the files are still on the drive as the drive is showing up with 41.7 GB used, even though there's only 3.16 GB worth of windows 10 files on the drive. This is a 64GB drive.

I'm not sure what happened, but can anyone please help me retrieve the personal files that were originally on the USB.

 

[SugarPsycho]

I am pretty sure an ISO rewrites USB files because it is a completely separate format for ISO files, you might be able to take it to a place where they retrieve data and they may be able to get it but other than that they are most likely gone. http://lmgtfy.com/?q=Data+recovery+services

 

[USAFRet]

When creating a Windows install on a USB, it specifically warns you, multiple times, that all existing files on that drive will be wiped out.