Check your Historic, go back to the day you changed your Avatar, just a few mins before & you should find it, yo!
Lost avatar picture, can't get it back.

Maybe you should contact support, then.
Turned out I had to. I couldn't get any other picture to work either.
Your old one went when you had the name change. There should be no reason why it shouldn't re-add on here. (that's what I meant on the homepage note).
Oh. I couldn't get it to re-add when I tried it several times yesterday. I thought I did everything right. I'm leaving for work now so I guess I'll work on it again later.