Didn't it run into the ex-Midland station of Lincoln St Mark's?
Perhaps it ceased when that station closed in May 1985?
It certainly did used to run to/from Lincoln St Mark's, but then it would do as that was the only station in Lincoln that was accessible from the Nottingham direction. In those days Lincoln Central could only be accessed from the east or from the Gainsborough direction. Trains were only able to run t/from Lincoln Central from Newark and Nottingham following the building of a new piece of line just to the west of Lincoln, which had to be built before St. Marks closed.