Shitty that this happened! This dude needs to get his tin can caved in!
Aside form that, you know a guy that knows a guy that knows him, correct? So, that means that he knows a guy that knows a guy that knows you. Meaning, if he didn't directly know about this thread, somebody has told him by now. So, if he is the guy that boosted your ride, he walks in step with your proclomations.
Honestly, I really hope you get your ride back but it is time to shit or get off the pot! (<--No offense meant) For your own sanity, do not hesitate for one more second. Every second that goes by (whether it was this guy or not) makes it that much more unlikely that you will ever see your ride again. I can also tell you that the biggest regrets I have had in my life are the moments that I sat on the pot and didn't handle my business. If he isn't the thief, you need to find this out ASAP so that you can move forward with other options.
As far as the police go, these guys are trained to see through the bullshit and the lies. If they knock on this guys door and question him, they will surely ask to look in his garage. Usually people in this situation will oblige, whether they are guilty or not. Despite what people say, most ARE intimidated by the law. It is only natural. If he denies them the chance to look in his garage, this gives them reasonable suspicion, reasonable suspicion usually means a search warrant. If they leave to get the warrant, you can then sit on the house and stake it out.
Regardless of your actions, it is best that the authorities know about this either way. The more details they have, the more useful they will be.
I don't envy your situation one bit but I can promise you that the sting of having waited too long to act will hurt much longer than the initial sting of having your car stolen. A man's regrets will outlive the pain of his actions, always!
Stay safe and best of luck.