The ornamental design for a surgical instrument for locating a facet joint.

FIG. 1 is a bottom perspective view of a surgical instrument showing our new design;

FIG. 2 is a top perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a left side elevational view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a top plan view thereof.