The man anonymously handed over a two-minute video of the operating system's features to Engadget before the phone, he says, was remotely locked and wiped.
It tours ICS's camera UI, a new Google apps icon that launches a menu with apps such as Google+, music, books and maps, app deck, notification bar and widget screen.
A new app launcher and app drawer, redesigned notification bar and Google-blue theme are consistent with screenshots of the operating system that leaked last month. But the story is a bit hard to believe. And the operating system could be a fake (although admittedly a pretty convincing one) even if the story about receiving it via eBay is true.
Gizmodo's Brent Rose points out that in the demo, the Android version is listed as "IceCreamSandwich."
"Never, in my two years of using Android have I seen something like that," he says. "Android version is always a number."
We've pasted some screenshots from the video below. Visit Engadget to watch it in full, and let us know whether you think it's the real Ice Cream Sandwich in the comments.