I voted family/friend/neighbor knows what happened.
I do believe she was abducted. Believe it had to be someone with knowledge of family, and the neighborhood.
I still hold the opinion the baby was taken to settle an unpaid drug debt. I think DB sat outside to "guard" the front door but that didn't stop it from happening.
The involvement of drugs is the only reason I can come up with to explain the parents' refusal to answer questions individually and the FBI's continued involvemnt.
JMO