Re: No Problem....
Well, the person that found it is actually guilty of an offence, and so they could in theory be arrested, charged and convicted.
The article states that the USB stick was clearly branded, and it was obvious it belonged to The Greater Manchester Police and that they would almost certainly want it back. By taking it home and examining the contents, rather than taking reasonable steps to return the object to its rightful owner, the finder is guilty of "theft by finding".
If I ever found anything belonging to the local constabulary, I'm pretty sure I'd return it straight away rather than risk getting on the wrong side of those with the power to make my life a misery.