Well the night they made out, the memory lost was due to drunkenness. The part about not recognizing him may be because whenever he saw jun, jun was normally wearing a mask to cover up the bruises on his face.
In addition to that, the author may just be drawing jun that way for us to see the resemblance, while this is not how jun is seen by him. Maybe the author can't change their drawing style too much in order to draw jun in a radically different way so that there is no resemblance (Or maybe it is just that all Asians look alike so he could never be sure if that was jun or not...)
Yeah, there was that thing bout face mask and all (also he saw him plenty of times without the mask), but srsly. Ah, I will accept if it will stay like this but somehow it is very unsatisfactory for me : / Just.. the guy has forgotten to much
I hope there is some explanation for the memory loss thing. Bcs now it just seems weird - looking totally different although he looks the same. lol. And then forgetting about the encounter later - is it some kind of brain damage? :D Even if a person undergoes some plastic surgery and grows up it should ring the bell a bit.
Just hoping ┑(￣Д ￣)┍