I would definitely give a shot. I usually, use same usb port on my external drive so that it gets same drive letter. While, everything works, I am beginning to think may be my hard drive is too old and its not handling safely remove action properly. Because, I never remove drive without "safely remove" action removes the drive letter.
As my last save data are not there in the geodatabase (as I inquired from R), this issue could have arisen during drive removal process. However, I don't know what file system you are referring to by "scoutcefiles."
I was always able to open project file directly from drive, there wasn't any issue. I can still access other geodatabses in the same drive, but not this one.
Thanks for creating your time for this issue.