I think that typically, part of being charged with receiving stolen property is that the purchaser must know that the property is stolen. I'd like to think that most people would not purchase stolen property knowingly but obviously the fact that there are laws against it mean that people do it.
But I also think it's better that law enforcement become involved in the situation so that hopefully the seller would be contacted by law enforcement and be able to either tell them who they got it from or, if they stole it, be charged. Again, it's not likely to work out that well in practice.
So Meraki would have a moral obligation to notify law enforcement if they were contacted by the purchaser of stolen property, they shouldn't notify the owner other than to ask for a file number that whatever branch of law enforcement has provided the owner with regarding the theft.
As for the buyer of stolen property, they'd be out the device but hopefully they would have used a method of payment that they could file a dispute with, like a credit card or paypal, etc.