Hi, welcome to the forum!
Freddy is correct, MusicBee is not configured to move anything "out of the box", you would have to apply one of the file organization commands for that to happen. And MusicBee does not do any deletion without your input.
If you can still play the files from MusicBee, then they are somewhere. MusicBee's database only stores metadata (tags, etc), not the audio files themselves. Take a look at the Properties tab of the tag editor, and it will tell you where the file is located. Or just right click and go to search, locate in Windows Explorer.
If you can't play the files from MusicBee, then whatever moved or removed them was outside of MusicBee anyway. I would investigate other audio programs or overzealous antivirus software.