Which is worse, buying stolen property, or stealing property? If they couldn't be accused of the former, they would be accused of the latter.
You seem to forget the very basis on which this was declared buying stolen property: the theft itself. The theft itself would have occurred no matter whether it was bought or not, and both parties would be guilty if it was just handed over.
Apple lost a phone. And the police busted someone's door down. I've read many stories of lost phones where the original owner, via software, has given the exact address of where the phone is, and what did the police do?? Nothing.
Since when is it the JOB OF THE POLICE to enforce self-inflicted violations of an individual corporations IP? This is not the role of the police in our society, it is as simple as that. It doesn't matter what is right or wrong, legal or illegal, they are not supposed to be prosecuting this type of thing.
"One who finds lost property under circumstances which give him knowledge of or means of inquiry as to the true owner, and who appropriates such property to his own use, or to the use of another person not entitled thereto, without first making reasonable and just efforts to find the owner and to restore the property to him, is guilty of theft."
edit:
Also relevant: http://jballer.tumblr.com/post/540967372/gizmodos-trade-secr...