It was all part of the plan, this was how he planned on approaching the boy...there was a reason for it. Number one, he doesn't even know the boy's name, so calling him Oliver wasn't a mistake.
He did it on purpose, and as said, there was a reason for it. The boy was still glancing at him with that expression on his face, and this time, he spoke out,
"I'm not Oliver".
"Oh! You look like a certain guy I know that is named Oliver, so I thought you were him. I and this guy haven't been in touch for a while now, and I've been noticing you for some time now. I was thinking you were him, but wasn't sure,
So I decided to approach you today to confirm, and I've confirmed".
..First of all, he dropped a big lie, he said he and Oliver hadn't been in touch for a while now, but they do see each other at school almost everyday.
And again, he didn't even bother to ask the boy his real name. The boy said he wasn't Oliver, he didn't bother to ask him, 'What's your name then?'.