There's a couple of ways to look for the frequency information in the FCC's ULS database.
You can do a query of all State of North Carolina licenses within the "YF" service, which seems to cover almost all the Viper trunked site licenses within the state.
You can also do a similar service query geographically, using the coordinates of your listening location, searching out to 30-40 (or whatever value you choose) miles.
Keep in mind that a site doesn't need to be in your county to possibly repeat traffic from your area. If a Viper radio monitoring your district talkgroup is affiliated with the site in Mount Airy, Sparta, etc., that site will air your district channel.
WQDE987 YF NCHP F Moravian Falls Wilkes
866.2500 866.8625 867.2250 867.7625 868.7500
WQEQ547 YF NCHP F Sparta Alleghany Green Mountain 866.3875 866.8875 867.5625 867.9750 868.7750
I cannot tell you whether either of the above sites have been reported as "on."
Listen to each of the five frequencies - in conventional mode - for the sound of a Motorola control channel. If you hear the control channel buzz, program the frequency in a scanner, using control-channel-only mode, and see what you hear.