Something Sheldon should know

The show: The Big Bang Theory
The episode: "The Creepy Candy Coating Corollary," first aired on CBS last night.
What happened: Sheldon (Jim Parsons) and Raj (Kunal Nayyar) sign up as a team for a card game tournament. I don't remember what Raj's reason was for joining the tournament, but Sheldon's was the opportunity to defeat Wil Wheaton (Wil Wheaton) in revenge for failing to show up at a Star Trek convention in 1995. Sheldon and Raj easily make it to the finals, facing off against Wil Wheaton and Stuart (Kevin Sussman). Sheldon is close to defeating Wil when he discloses the reason for his animosity. In response, Wil says he failed to show up to the convention because his grandmother died. Sheldon immediately changes his tone and throws the game. Wil makes the winning move and then claims his grandmother did not really die, and gives a frivolous reason for not showing up at the convention.
Why it doesn't quite make sense: While it's true that there are gaps in Sheldon's knowledge (he doesn't know about Radiohead, for example), I find it quite surprising that he knows Wil's nickname for his grandmother, yet doesn't know whether or not she's still alive. The real life status of Wil Wheaton's grandmother is irrelevant for this nit (though I must admit I'm curious). Whatever it is in the semi-fictional world of The Big Bang Theory, Sheldon should know. If in 1995 Sheldon was really so distraught over Wil's no-show, wouldn't he have endeavored to find out what happened? In the process, wouldn't he have learned something about the Wheaton family? Even if he didn't, the episode establishes that Sheldon has a photographic memory. (Eidetic memory, whatever). Doesn't Sheldon subscribe to at least one Star Trek fan publication? Surely one of them would have explained why Wil failed to show up at the 1995 convention.
Lastly, I find Sheldon's decision to throw the game somewhat out of character. Sheldon is not generally known to agree to conciliatory gestures suggested by others, much less come up with a conciliatory gesture on his own. Wouldn't Sheldon instead have won the game anyway, if not for revenge then at least to show his superiority?