ITA. If they had Gabe hidden somewhere, then why not stop the whole thing, come clean and try to minimize their "guilt" in the whole deal by saying what they have been saying: "We thought the father was abusive, we agreed to give Gabe a better home, etc."
Unless, as you said iluvmua, either Gabe went to another couple entirely, or what if someone else is holding Gabe for the Smiths right now? But if so, wouldn't THOSE people be afraid and come forward?
If I was holding Gabe from either the Smiths or another couple I would come foward and tell LE everything I know. so far no one has done that and I fear that Baby Gabe is no longer living.
If a girl or some couple just decided to hand over an eight month old baby because they did not want the child for whatever reason. I would have some SERIOUS questions.