I agree about the case being tight. However, the car thing, at least no further mention of it, stuck out like a sore thumb. I would assume that they would check vehicle registrations to see if the suspects or people in the family/co-workers/friends/neighbors owned that kind of car. (I mean that in the sense of the suspect's could have possibly borrowed a car from someone). The detectives were like, "the camera didn't catch the the license plate" THE END.
Side Note: Many times on other shows, even though it is tedious, detectives/investigators will (especially if they have murder time established), check all exit route directions for a few miles. They check for any public and/or security cameras on businesses to see if there is any possible recording of the specific vehicle passing by.
Oh well, they seemed pretty diligent. They have probably checked it out and it led nowhere or it's something that they are not releasing to the public.
