I don't think the wizard part was towards Conan. Because Sera showed her brother Conan's picture in the first place, so why would he ask "Did you met the Wizard (Conan)"? Sounds strange kinda.
If it's about KID, then Sera did meet KID in two cases. One case where KID disguised as Sera. The other case was the Train case, tho I don't know if Sera figured out KID at that time.
During the train case, Okiya/Akai would know that KID was there too. If Bourbon could know too maybe.
I don't think KID would be in that case, because if the brother would be hinting at that with the PS., then he would have to be around them to know that one of them is KID disguised.
But if the wizard part is aimed at Conan: Koumei compared Conan to Zhuge Liang. And according to wiki (http://en.wikipedia.org/wiki/Zhuge_Liang
), in fiction he was "described to be able to perform fantastical achievements such as summoning advantageous winds and devising magical stone maze", so kinda like a wizard?
Maybe that helps? :3
Also, Koumei and Shuukichi actually have similar/same eyes D:
Other question not directly related to the case:
Why was Fake Akai disguise with a cap first and then that hat? Akai and Rye were always wearing a beanie (at least what we saw). If Vermouth is a professional in disguises, why would she change the headgear to something else? Does that have any meaning? O_o" Or was that maybe just so, that Sera is still wearing the same hat even tho she got her "brothers" hat now.