Yikes -- sorry to hear about that.

If you called in regarding a reservation I think CO keeps track of when and who changes/views them so I think there's a paper trail, albeit in an electronic form. That said I suspect the UK (or greater Europe) desk is not as large one of the SLC/IAH/TPA centers so I'd wager you'll be able to get close with just the first name and not have to resort to digging through PNR history.

What I'd do at this point is download skype (or whatever VoIP software you want) and call 800-we-care2 to report the agent. Don't expect anything but at least the bad apple will hopefully not surface again.