The visible role is the disguise
The Drunkard rule is about an actual Meddler hiding under another good role’s display. “Not in play” concerns that displayed role’s actual identity in this case; it does not mean the suspect list cannot contain its name.
A card showing Mathematician could therefore be a Drunkard supplying an unreliable total. Check the permitted role pool and other statements rather than assuming the displayed role’s ordinary information is valid.
When the arithmetic works but the premise does not
Imagine a displayed Mathematician says 7 and you enumerate all four sets for addresses 1 through 6. The calculator has done its job correctly even if that number came from a Drunkard. What failed was your assumption that the announcement described the real counted addresses.
A historical player question about a puzzling Mathematician was answered by pointing out the Drunkard disguise. It is an example of this failure mode, not a guarantee that every incorrect-looking total has the same cause.
Do not treat every good disguise as a Drunkard
The Copycat instead uses a good role actually present in the case and does not add the Drunkard’s lie rule. Distinguishing these disguise restrictions can be more useful than merely finding a duplicate appearance.
Your next step is to ask which actual role could produce the display and which information rule it would use. If your only evidence is a bad statement, keep alignment open: Drunkard demonstrates why “false clue” does not automatically mean “evil arrest target.”