[Freeswitch-users] X-Headers on BYE- How to save?

I have a carrier supplying the LRN in the BYE / OK to my BYE. It SEEMS that when the other party hangs up first, I get a sip_h_X-LRN in my xml_cdrs, but not when my FS hangs up first. Presumably this is because their bye happens before the reporting begins, but my bye starts reporting before the OK to the bye is received. So, how would I be able to save access this header? A hangup hook of some sort.. well, that won't have access either. Any ideas? Thanks, -Avi