Hi John,
there are two stories here: Bridge and Lightroom Classic. I'll start with Bridge.
it is impossible for Bridge to make your files disappear. The files are SOMEWHERE on your computer. I suggest you search by date or something, anything to find the files on your computer.
FWIW, I think we've all did an "oops" while moving something and the hand jiggles at the wrong time and you inadvertently let them fall into another folder. BUT THEY ARE NOT GONE!!
Now, LRC: LRC is a database and it works by knowing where everything is. It doesn't make a difference where things are as long as LRC knows that location. If you move things in the Finder/Explorer than LRC doesn't know about that move and you get that exclamation symbol. Once you find the files and re-link them, you'll be good again. But this also means that your original action of moving the files outside of LRC was gout to cause the same end result.
do a google search for "how to find missing images in LRC, you'll find a lot of answers because this is a common issue that people have until they stop moving files that are part of LRC while in the Finder/Explorer.
I hope this makes sense, good luck finding your files, they're somewhere.