Good, thought Zacharias as he said, "Oh, that's alright." He had been going for mostly unnoticeable and unnoteable when he'd dressed in Muggle clothing that morning -- simple blue jeans, dark blue jumper, and a (currently unbuttoned) black peacoat. Although he'd worn more Muggle clothing since leaving home, he still didn't wear them often enough to feel comfortable wearing them. He always wondered about making a Muggle fashion faux pas and being found out, in some form, as someone who didn't belong. Of course, he reasoned this man could have not noticed him simply because he was too lost in his own thought, which, to be fair, had been why Zacharias hadn't noticed another body with another hand reaching for a book on the same shelf.
"I should have been paying more attention," he added by way of apology, and he silently chided himself for that as he took a step back to give the man more personal space. But he'd gotten lost in trying to find a book or two to read, in that grim determination to not leave the Muggle bookstore empty handed. It was stupid since he didn't necessarily need more books, but then... part of him did. If for no other reason than because he needed something to occupy his mind during his lunch hour. "But, please," he said, waving toward the bookshelf to indicate that he'd wait his turn to while the other returned to reaching for his book.