Observer suddenly realizes that Adhesion and Cohesion are totally different things, and making that mistake was stupid.
I like the idea that he used it to block the Chasmfiend claw, and adhesion is something he might have been using little bits of from time to time, but I doubt it was much. Shardplate seems to mess with Lashings too much, and WoB is that sucking the Stormlignt from Shardplate is really hard, so Dalinar would have to have those spheres on his person. (If he was taking it from Parshendi or during the skirmishes, they'd have noticed and taken them off, like with Kaladin)