Gonna be brief here, since I don't remember enough of this to actually remember what happened, exactly, but what I do know is:
At some point, I think a few weeks after the t3 mission release, I got a darkfang shield as a drop. I wandered around haven for a bit thinking of what to do with it. I considered just vendoring it, but since it was an unbound 4* shield I decided against it, and asked my guildies if it was worth anything. They said they didn't know, but imagined not. I checked the AH and there were no darkfang shields to compare it to, so I assumed it wasn't worth very much seeing as it was underused (I had no idea it lacked a recipie). I don't remember whether I vendored it, or made some lucky person on the AH very happy, but I do know that I lost 25kCE-50kCE without realizing it for three months.
Just thought I'd share that... because I find it hilarious.
Since August, the wiki page has said that it's a "rare drop". If only you'd checked the wiki, you might have realized that it was at least somewhat precious. Bummer.