Ita!
I never second guess what the officers did or the decisions they made at the time.
Only they know why certain decisions are/were made since they are the only ones privy to all of the facts in evidence. Imo. FBI profilers told them not to do so because it may profoundly affect Jayme's chances of remaining alive.
Just like the PC knew the Washington DC snipers didnt drive a white van all along. It was designed to fool the killers into believing the police really has no clue what they really drove, but of course they did.
Decisions like this are common, and each one has a valid reason for doing what they do.
I can only make a logical guess, and they did not want the kidnapper to get spooked in any way whatsover.
If the kidnapper knew they had put a description out of his vehicle the police knew he could kill Jayme, and then flee.
They always firmly believed Jayme was alive, and they didn't want to do anything on their part that may jeopardize that firmly held belief.
Were they looking behind the scene? More than likely but trying to find one is like looking for a needle in a haystack when they didnt even know which haystack to even look in.
Didn't he even change license plates, and the tag number wasn't captured when the officer saw it?
Imo, it's so easy to Monday morning quarterback from afar when we aren't any part of any investigation, and aren't aware of any of the details or why certain decisions were made, and why, by all of those who were actually deeply involved..
I believe withholding this information from the kidnapper gave Jayme a much better chance of survival, That was Fitzgerald's main goal from minute one.
It worked, because he had relaxed thinking he had completely gotten away with double murder, and kidnapping.
Putting out the description of the car the kidnapper drove would make them even more unstable/panicky, and thinking he had to kill Jayme so no living witnesses would be left behind.
It could have cost Jayme her life. It was a gamble Fitzgerald, and the profilers weren't willing to take.
The best way to keep this monster calm was for Fitzgerald to announce over, and over again they had no evidence or clue who the suspect could be.
Imo