I'm fairly sure there's no 'hidden' list of old Bluetooth connections. Generally Bluetooth can only remember 7 connections to a given phone and 'forgets' the older ones as new devices are paired. If you've deleted them, they're effectively gone forever. If you'd like the technical details, PM me and I'll send you some links to relevant documents (or I can send you some Academic Papers if you prefer).
I've recently graduated with a Bachelor's (2:1) in Computer Security & Forensics. My dissertation was investigating the current state of android security.