The problem was that the courier website was saying they'd been delivered when no one was even in any of the offices on my level. I called the courier service and they were sure they'd delivered it so I emailed the website and told them the shoes never arrived.
After a few minutes of door-knocking I found the shoes down on level one where someone had signed them in and forgotten to come deliver them to me.
When I got back to my office I saw that the website had refunded me the full amount and after some discussion didn't want the money back.
Wins all round!