I thought they were only on MOPAR, but some ________'s are built with moving outer bearing surface(socket) the ball is the inner bearing surface. Try using a tiny pair of Vice Grips to hold part that zerk screws into, or wedge a small tipped screwdriver in gap to keep it from turning while zerk is removed.
Anyone who doesn't understand above needs to go to MOOG or TRW site and find cutaway view of ball joint. MOOG is especially proud of their "Problem Solver"tm. ball and socket line.
iceberg,
Have you consulted shop that did repair? I'd expect they would want to clear any issue instead of loosing a future customer.
Bob