Green’s Dictionary of Slang

(drugs) when taking a drug, usu. heroin, cocaine or crack cocaine, searching for every particle of it.

1992		T. Williams Crackhouse 78: As proof she talks about ‘ghostbusting,’ the practice of looking for white particles on the floor.
2001		ONDCP Street Terms 10: Ghostbusting — Smoking cocaine; searching for white particles in the belief that they are crack.