Perhaps. But if you mean the 'bourbon' Okiya was drinking, then the argument could be used on either side. The FBI clearly conversed about how Shuuichi's favorite drink was bourbon. Also, Haibara received chills around Shuuichi just like any other B.O. member. He WAS once a part of them.
It hints that it could be bourbon due to the fact that Okiya bugged Agasa's house before, but at the same time, Conan trusted this man too much, wouldn't you think? Why would Conan allow a Black Organization member into HIS house, let him know that Kudo Shinichi IS alive, especially around Haibara? If you noticed in the manga
[here]. If he'll show such urgency when there is a hint of the Black Organization being risky, then why would he also freely deduce in front of and suggest rides from Okiya to Haibara?
Plus, just Shuuichi not have removed his disguise for a day? Perhaps he had a reason to strip of his disguise on that day and just happened to catch a spot of bad luck.