I think that Ricci slowly percolated to the top of the list of potential suspects. In the initial interview I would bet that LE probably knew nothing about the Jeep that Ed had sold him. The Smart's probably gave LE a list of anybody who had worked on the home or looked at it while it was listed. If Ed had been suspicious of Richard from the beginning then I'm sure he would have gone over every single detail of their business relationship right from the start. Ed didn't even know Richard was a felon. He had suspected that perhaps Ricci had stolen from him, but Richard had returned to Ed and tried to con him into believing that he wasn't the culprit in the thefts. Also petty theft is along way from kidnapping. It just seems to me that the details of the Jeep sale came to LE's attention from a follow up interview by detectives after nothing really jumped out at them in their initial interviews with potential suspects. By then it was to late. The Jeep was back at Moul's.
First, we don't really know that Ed didn't know he was a felon. I wouldn't blame Ed for not admitting it now if he knew. If I had someone kidnap one of my kids and there was someone in my life with this kind of a relationship with the Jeep and all that I had had to terminate less than a year ago this would be on my short list as the press indicated Ricci was. And LE should have run a quick check on this short list and seen Ricci was a career criminal before they talked to him and should have been tailing him, IMHO. They had half the SLCPD working this case.