Interesting challenge.
I've not tried setting the mgmt interface to the IB network instead of the eth cable one yet, just in case I locked myself out.
Have you tried scanning entire subnets yet with something like nmap, to see if the mgmt port is showing up somewhere unexpected? Also, do you have a dhcp server it could have picked up an address from? Not saying it has, but might be worth checking.
Side note - it's generally better form to create a whole new topic for a new problem, instead of grabbing someone else's. Reusing threads can be a pain when someone's searching for results through existing postings. Something to remember for future.