Comets’ orbits around the Sun are not reliable.
While the paths of more than 100 short-period comets have been mapped or tracked, astronomers can suddenly “lose” a comet.
Sometimes it is simply gone. Other times, when it is found, it isn’t always as expected.
The Wilson-Harrington comet, discovered in 1949, was expected to return in 1952.
It wasn’t seen again until 1979, and then it came back resembling an asteroid instead of a comet.