Watchmen came out almost a decade before Comic Sans existed, it was hand-lettered by Dave Gibbons. In fact, it directly inspired the creation of Comic Sans according to Wikipedia.
You're not an idiot-- That distinction isn't discernable from the name per se, that information is concealed within some relatively obscure typography lore!
Although many people believe that the "Comic" in Comic Sans refers to the lettering common for comic books at the time, font designer Brian Richardson revealed that this was not the case: While speaking on a panel at the 1999 Microsoft DesignTalks conference for designers, he said "We just wanted to make something fun, that people could use to inject a little bit of humor into their documents. It was actually called 'Funny Sans Serif' during development, but Pat convinced me last minute to change it to "Comic Sans" so that it would appear higher in the font picker."
Now, Wikipedia doesn't tell you that because I just made it up, but it would be totally plausible! Then some of us would be talking about how we thought it was about comic books. So you're not an idiot, IMO.