Most things 'bike' were invented in the late 1800s before they were forgotten and then re-invented more recently, so I wouldn't be at all surprised if disc brakes also turned out to be one of these.
Wikipedia says:
"Disc-style brakes development and use began in England in the 1890s. The first caliper-type automobile disc brake was patented by Frederick William Lanchester in his Birmingham, UK factory in 1902 and used successfully on Lanchester cars."
This suggests that the first disc brakes were made in the 1890s, but were not used on cars before 1902 - could these first disc brakes have been made for bicycles?