It is one thing to have the stolen item taken away from you (which happens often and you lose having paid for it) but it is another thing to be accused of knowingly purchasing stolen item or be part of the actual criminal conspiracy. I tend to believe your friend left something out from the story (DAs typically would not waste time on accusations they won't be able to prove), but it is also possible he is a victim of unusual circumstances.
This. It's difficult get cops to respond to most burglary or break in calls, they just want to take down info over the phone.
There may be missing details, or your partner may be fighting human nature, the more he screams the bigger the over reaction.
It's like DUI---the rich don't care if they get caught, they beat it with big $$$ lawyers, and the economic consequences aren't a big deal if they don't. The poor don't care, they don't pay fines, there's no room in jail and they normally drive without licenses and insurance anyway. But, it's a serious issue for the middle class, and most of the good feelings cops and DAs have about enforcing DUI are driven by middle-class anguish.
Unlike DUI, buying stolen articles doesn't usually harm others physically, and I can't imagine that any jury in the country would convict this guy if his version of the truth is even remotely correct. He's either holding something back, doing things that enrage cops and DAs (really bad and disrespectful idea) or playing into "go after the guy who cares" syndrome. The DA might be able to convict the guy who sold him the amp, because he knows he's not going to jail and doesn't really care, but that's not much fun for cops or DAs.
I doubt that there's a lot in our increasingly liberal/prison-space-challenged society that's much fun for law enforcement and DAs, and while they may not have the "guilty until proven innocent which never happens" power of the FAA they can make choices, and your partner may want to consider if there are other ones that he could make that might help deescalate things.
I've heard of acrimonious lawsuits related to people trying to keep articles someone else claimed were stolen, and it's not easy to prove that something like an amp was stolen from you in the first place. It happens with airplane title disputes, in fact. It's not easy to get property back, much less prosecute an "innocent" buyer. I've never heard of someone being prosecuted for buying stolen goods unknowingly, and how exactly do you prove that they knew it was stolen?
This doesn't sound like something law enforcement and ADAs would waste time on, there isn't enough tough-on-crime press to be had and law enforcement is bogged down with real crime. More like something a city would be sued for wrongful prosecution over---guess I'm just skeptical, but something doesn't add up.