It may have been slightly mis-reported. If the pilot is uninjured and able to make a report, and there's nothing particularly mysterious, then AAIB will often only take a few hours to say "release the airframe and send us a report, but we won't send anybody out". It then usually appears as a short 1-page report in a later monthly AAIB bulletin.
That said, if it was an (initially) unexplained engine failure, leading to substantial damage on landing I'd have thought they'd want to take an interest.
G