Are you sure it was SCHP, and not another agency being received via skip ? The low band skip conditions have been fairly decent here recently.
California Highway Patrol uses 42.34 for statewide notifications and emergencies.
Illinois State Police use the frequency for dispatching in a couple of ISP districts, although they are transitioning to 800 MHz at this time.
I believe Washington State Police also use 42.34, but I never have logged them.
The State of S.C. continues to maintain the low band licenses, so one could presume they might put the channels back into service under some circumstance, such as a weather-related disaster that takes down part of the Palmetto 800 system.
Another possibility is that you may have heard a couple of people who purchased used State of South Carolina low band equipment. There was a "ton" of gear available at Shelby and other area hamfests last year.
At Shelby, two guys from Greenville were selling a trailer-full of the transceivers, minus control head and mike, for $5 a piece.