Unfortunately, it wasn't as much of a revelation for Sam like the fact that dragonglass was resting at Dragonstone, and he threw a massive hissyfit. One user on YouTube says: "I like Sam but he's an idiot in this scene for not researching further immediately. Worst timing for throwing a tantrum."
Another adds: "He is going to remember this later on and then have the same reaction we are all having."
Sam is just pissed that he has to rewrite all the old manuscripts because they're falling into disrepair. But towards the end of the latest episode, Sam and Gilly pack their bags and leave the Citadel, with Sam saying: "I'm tired of reading about the achievements of better men."
Hopefully he remembers that tiny bit of information that Gilly inadvertently highlighted, if he crosses paths with Jon again later in the season.
