You're taking it from the point of view as someone who posts on Hacker News that knows a lot about tech. At some point, not too soon after the theft took place, that prototype was in that house. Since Apple hasn't been able to track it since, the logical conclusion is that whoever stole it became aware that it can be tracked and turned the phone off.

The story that you're creating only exists in movies. Only someone as devious as Keyser Söze would do that.