Most likely the person won't be posting. You might want to try to send a tell to Doubt with your request, but only God knows how often the character is played, or if they would be willing to give up a name that might have had forever.
Maybe try type /getglobalname,Doubt and see which global owns the name and then try send them an offline message.
I did it for ya, since I'm at school waiting for hubby.
The global for that name is @Ipaku.
Good luck.
It's not me, I have no Doubt.
(Just couldn't resist.)
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TY, Vivace and Saga! That was very kind of you. I know it was a shot in the dark, but I didn't know how else to find the person. I'll try sending them a /tell right now. 
If you would be willing, I would like to discuss "buying" the name from you, in some form or another. I would REALLY like to port over my Doubt toon from another server, but the name is tied up already; and I can't really change the name, as it is part and parcel of the character concept.