PROJCS["NAD_1983_StatePlane_Missouri_East_FIPS_2401_Feet",
GEOGCS["GCS_North_American_1983",
DATUM["North_American_Datum_1983",
SPHEROID["GRS_1980",6378137,298.257222101]],
PRIMEM["Greenwich",0],
UNIT["Degree",0.017453292519943295]],
PROJECTION["Transverse_Mercator"],
PARAMETER["False_Easting",820208.3333333333],
PARAMETER["False_Northing",0],
PARAMETER["Central_Meridian",-90.5],
PARAMETER["Scale_Factor",0.9999333333333333],
PARAMETER["Latitude_Of_Origin",35.83333333333334],
UNIT["Foot_US",0.30480060960121924],
AUTHORITY["EPSG","102696"]]
This is what I am seeing from spatialreference.org. It looks like the unit of this projection is in feet, which means that your measure tool, buffer, distance tools, etc., will also use this unit.
The easiest answer, as I see it, would be to make a custom projection based on this one that uses yards instead of feet. I was able to find this blog post about someone customizing a WKT projection to use meters instead of feet, which hopefully you might be able to emulate.