Whatever it was, there's no trace of it on the FR24 website, at least not in the last few months.
A more accurate description of the problem would have been finger trouble on the part of the crew when entering the ACID (Aircraft ID, in practice the flight number) into the FMS.
That gets used within the Mode S and ADS-B transmissions, and the enthusiast tracking sites use it to deduce what route the aircraft is flying. They typically don't do any sanity-checking, so if a flight is over the Med but sending a flight number of a transatlantic flight, it's the latter route that the site will show. It may well be corrected retrospectively if someone happens to spot the error.
Having said that, LH FRA-MLA flight numbers don't remotely resemble LH442.