The lack of serious searching for RFG seems to make this possibility less likely, in my mind. Surely, if LE even suspected it was drug related and a revenge killing, the response would have been more?
The no sign of luring via Internet or phone is also ok with me as I've hung out in a courthouse and watched the comings and goings. RFG could have been approached quietly and the message passed to him, verbally or note. Although, I feel pretty strongly that IF that happened, RFG would have told someone where he was and what was happening. It's not a meeting he would have taken without someone in his office or working on the case being told, IMO.
According to the Informant, there were other people working on the drug ring (or whatever) investigation, including the AG. A couple of them were probably aware of Ray's plan to meet with someone promising to provide more information. When he disappeared in Lewisburg, the AG probably surmised he was killed and why and decided to stay silent. They didn't trace the murder back to the criminal ring because they didn't want to meet the same fate. So they turned Ray's missing person investigation over to a small town police force with only 1 part time detective and made sure Ray's case went cold. Just a guess on my part.
Alternately, the AG or others involved may not have wanted the public to find out that the DA was killed in an investigation gone wrong.