Sigurd is already waiting at the parlor by the time he sends the message, so if Björn plans on standing him up, then he's already a bit too invested to avoid such a thing happening. When the other arrives, he'll see Sigurd in a table in the corner, nursing nothing more than a glass of water for the moment.

He hadn't really expected to have this happen.

Actually, he was rather shocked by it, to be truthful. And he wasn't often caught unawares by things like this. It comes from being a rather quiet, observant sort. That said, it's difficult to observe certain things on the Internet, it would seem. It requires an outside eye to notice one thing or another. An outside eye which Sigurd did not possess, where his best friend did.