I recently ran into a similar issue. I found out that ”artefacts” of an app (not the app itself) was on a external drive->disk image of a drive i had rescued earlier for a friend of my father, was picked up by Mac App Store as it was installed on my actual boot drive. The app, which also happens to come from a fellow developer from the same country and with similar named apps on MAS, came to my the computer after the person installed adware/malware from some ”system cleaner application”, and when he searched for ”Video player mac”, all search results pointed to a application at the Mac App Store, which was no accident.
Could it be something similar (ex. connected a external drive)?