Are you getting an error message and if so, what is it?
No message when I play the thumbnail. When I try to open I get The alias “Spokane 022 (110 of 7177).MP4” can’t be opened because the original item can’t be found message
Now I'm more confused. If that is an alias, it isn't much help to recover it if it can't find what it is pointing to.
As Chas said, recovering thumnails likely isn't any help either.
To use the Terminal is tricky to explain...
First the BIG WARNING: You can really mess up your system with Terminal commands. Don't try to get fancy with other files and folders.
Open Terminal from the Utilities folder.
Type 'mv ' on the line, without the quote marks and add a space.
Open the Trash.
Drag a file of interest to the Terminal window and drop. The full name with path appears.
Hit the space key again.
Type '~/' on the line, again, without the quote marks.
Hit the return key.
What we just did was move the file to your home folder.
If you get an error, STOP, and report it back.