Jamicat,
First off you are ASSUMING that LE did not talk to him. I've served many search warrants in my career and have always tried to talk to the person first. They could not hold him or his roommates at the apartment. It does not mean that they were not watching him when he left but they can't exactly follow him to where he went and start questioning him again. No doubt if they handled it the way you would have liked, you probably would have found something else to nitpick.
If Matthew had nothing to hide he would have talked to investigators that day. I know if someone came to my door to search my car I first off wouldn't leave the location where my vehicle was, I would talk to investigators to clear my name, and would ask what I could do to help...
No, I am not so assuming. LE did talk to him and his roommates. Also, yes, I agree JM's reaction was not normal. At this point, I'd have gotten an attorney involved immediately and yes, I'd have watched them search my car, not disappear But then we don't know what LE told them that they disappeared as they did. Though we like to say this is not about race,black men do not fare well in criminal investigations. But I am surprised that LE did not have resources to follow the owner of the car that is so important that a search warrent was issued for it. The person could talk, a girl is missing, could still be alive, anything possible to get him to give info should have been the concern, not turning a back on the guy which, yes, LE did. For all we know Hannah could have been a live somewhere at that time.,maybe they went off to finish her off and truly hide the body now that LE was right there. Car wasn't going anywhere. The people were and did. Even if JM took off, the roommates might have cooperated given the seriousness fo the situation. All three men just left. At this point, it would be understandable if none of them talked.
You are right that we do not know how investigators approached the men. I would hope that they pretty much begged for the men to please talk to them--not gone straight to the car, but tried to get any info out of those men, explaining that a girl's life might be at stake. Please, any and all info about wherabouts, did you see her, etc, etc before proceeding with the car search, and then making sure all three men were followed when they left. THey did not flee--that would have been released, they just left. I think LE could have done more there.
A lot of what actually happened will likely come out later. I think the car was on the LE agenda as a prize not just because of Hannah's disappearance. I don't think Hannah was the focus when they went to the apt with the search warrent. SOmething about the car really had LE hot.