I do not wish to clutter up the bad guys thread but donniekak, even if you don't think you'll see your ECU again, if you haven't already done so, REPORT IT! I know people think that cops do nothing but the truth is we cannot do anything without evidence. You may not think you have any (or had any) but you would be surprised. You have a confirmed address, you have the Craigslist advertisement. Presumably you have copies of correspondence with this guy? What about the box he sent you? What was he supposed to be trading? How much does that item weigh? If the box was posted, it was weighed (Post Offices do that!) so do the weights match?
I don't know much about your laws in the US but my understanding is that any theft or fraud across State lines and involving the use of the US Postal Service is a felony and certain 'larger' agencies are likely to be interested. Not to mention the fact that just because your ECU may no longer be in his house it does not mean other victims' property is not.
I understand the purpose of the Bad Guy Forum and I realize you wish to simply warn other members of a scammer even if you have no other legal restitution, but don't give up. What was he selling the ECU for? $150? More? Visualize him sitting in a restaurant with a few buddies having a beer, eating pizza and entertaining some ladyz on your dime. Now spend 20 minutes putting what you have on record together and go speak to someone.
You are reporting the THEFT of your ecu. If he wishes to claim he sent you an item in return then it becomes HIS responsibility to prove it. If he has proof of postage GREAT! Ask for the recorded weight of the item shipped. This kid clearly is not a professional and you have a chance to do something about this and stop a potential scammer. Even if there is insufficient proof to prosecute, I assure you cops turning up at his door asking about that ECU will be a better deterrent than a few words on here.
BTW that screen shot that Polish posted. The photo on the far right of the first row belongs to DR1665 I believe, another Arizona member. I can't read what it says in the bottom right hand corner of that photo but it looks suspiciously like it says galantvr4.org which means he pulled it off this site or got it from someone who was on this site. Now I don't know about the rest of you guys but I don't feel happy about kids scamming stuff being on this site and perhaps we should be doing something about this?