If if happens again - STOP - Move the handle bars from left to right (Full lock) back and forth to see if they come back. if they do - it is a possible problem in your wiring harness or plug under the tank
You can check fuse 3 but sorry to say with this vintage of clocks there have been quite a few failures of the speedo itself
I have a set of bad clocks for analysis loaned by one of the members but to date have not come up with anything