I'll assume that by "showing up in the JSS as an App" you mean "listed in inventory for one or more device(s)" and not listed in your App Catalog.
You might want to physically inspect the device to determine if it has been jailbroken. Jailbroken devices can install any number of unsigned apps with crazy names like "Fail Videos for whatsapp gratis best shazam pou hay day rush saga candy pet bitstrips tweetbot emoji emoticons iphone ipod ios7 ios8 music akinator talking hablador my plus pic game games sex vine tom stickers tomtom amazing great epic gopro go cam easy."
