I haven't seen it since then either. In fact, for a few weeks there, I wasn't seeing any ads. They only recently started showing up again on a semi-regular basis.
Try finding the ad using a secondary account if have one. I couldn't find the ad on my main Gold account. Switched to my free account and found it. The ad mentioned some snowball fight game. Get the ad and sign-out of that account and then into your main account to get the avatar item.
[quote name='CodeTrader']Try finding the ad using a secondary account if have one. I couldn't find the ad on my main Gold account. Switched to my free account and found it. The ad was mentioned some snowball fight game. Get the ad and sign-out of that account and then into your main account to get the avatar item.[/QUOTE]