You have made a good point, danny, and I was being, I believe, a bit too simplistic. Section 3(1) of the Theft Act says this:
“Any assumption by a person of the rights of an owner amounts to an appropriation, and this includes, where he has come by the property (innocently or not) without stealing it, any later assumption of a right to it by keeping or dealing with it as owner.”
Which is exactly what you said. Fudiot’s friend did come by the property without stealing it but has now (arguably) assumed rights to ownership.
What Fudiot’s local police officer will make of the matter is a bit hard to tell. But I still believe the best chances of success lie down the civil route. Fudiot would have no control over any action the police may or may not take (and I doubt they’d be interested in all likelihood). Whereas he would control any civil action he decides to take.