Ollivander overlooked the emotions that Dennis was expressing; he some times overlooked such things when his mind was focused on something else. At the moment, it was confusion, without a tinge of accusation.
"Why in the world would your brother have to steal a wand?" He began thinking out loud. "I know that I was kidnapped and tortured by Voldemort and the shop was closed," he said, as a matter-of-factly, "but surely there are other wand makers that you could've sold you a wand!"
The wands that Ollivander sold were considered the best, by far, but his shop was not a monopoly and there were other wandmakers in Briton.