Thorin hadn't wanted to visit the elves, but after Gandalf had tricked them into taking the secret path to Rivendell, he'd had no choice but to go with it. What they hadn't counted on though was that the path would be too narrow for Bombur.
Grumbling about the delay, and the fact that most of them had been forced to climb over (or find some other way around) Bombur, they stood about uncertainly. They were lucky in that he had gotten stuck just before the path opened into the valley of Rivendell, but now they had the difficulty of what to do. Did they leave some dwarves behind with Bombur? Or did they go ahead without him? They chose the latter; they were within the borders of Elrond's realm after all, and it wasn't likely that he'd be attacked during their absence.
"Don't worry, Bombur," Bofur called back cheerfully as they started to leave. "We'll be back for you!"
Gratefully accepting Elrond's offer of food and rest, the dwarves began filing after their host. Gandalf went first, followed by Thorin (with Fili and Kili immediately behind him), but the rest had yet to start walking up the stairs when Ori grabbed Dori's arm to get his attention.
"But what about Bombur?" Ori asked; his voice hushed so the elves wouldn't overhear him.
"We should go get him," replied Dori, also whispering.
"Let's send the elves," Dwalin suggested.
"Who's going to ask them?" wondered Dori.
Gloin elbowed Bofur roughly. "He's your brother," he growled sharply.
"I, ah, all right," Bofur replied, nervously approaching Elrond. Swallowing, for who knew how these high and mighty elves would react to his request?, he raised his voice so he could be heard. "Um, one of our dwarves got stuck on your path," he said hesitantly.
Elrond glanced at Gandalf in surprise, but Gandalf avoided his gaze. In truth, he hadn't forgotten, he'd just been waiting for the right opportunity to bring it up (admittedly, that would have been shortly after being seated).
"How did this happen?" Elrond asked, turning back to the dwarves. The only possibility he could imagine for such a thing happening was that their companion must've been badly wounded.
"Your path wasn't wide enough to accommodate our dwarf," Balin answered.
Elrond and Lindir shared a startled glance. Shaking his head slightly, only enough so that Elrond would see it, Lindir was already starting to regret letting the dwarves come in and was wishing that Elrond would send them away.
Finding his voice, Elrond instructed Lindir, "Assemble some elves to go get their dwarf."
Lindir nodded and hastened to obey.
"Shall we continue?" Elrond offered.
As they started following after their host once more, Thorin hissed to the wizard, "Gandalf, I would've thought you'd make mention of it."
"I would've," Gandalf retorted, "…in due time."
Note: I apologize for this one, I couldn't help but poke fun at Bombur. The name "Fat Man's Misery" comes from a place in Mammoth Caves (for those who are familiar with it) where the path is especially tight, and every time I see the scene where the dwarves are entering into Rivendell I can't help but think of that name (and it seems fitting with how tight that secret path is, its enough to make anyone claustrophobic).