MS 4 disappears

Musescore 4 is gone from my HD. 1,2,&3 are still there. Everything from program files and appdata is gone but the mus4 folder under Documents is still there. Luckily I backed up with a full disk clone. I can either slip the cloned disk in or copy the missing files which is a lot easier since I don't have to open the puter.

But does anyone know how a program could be deleted without going through the normal delete process? It is just scary.
John