I can verify that I've heard plenty of SCHP Spartanburg dispatch off the Spartanburg site, which is in Troop 3, since this thread was started. But I generally don't monitor other Troop 3 dispatch channels. So I can't answer your specific question about Anderson dispatch.
SCHP is using more channel patching these days, including in Troop 3. This means that the Dispatch talkgroups are being joined together by the dispatchers at the console. This is because they don't always have (or ever have) enough dispatchers working to cover each dispatch channel simultaneously. So they patch talkgroups together so that a single dispatcher can handle multiple dispatch channels. When a patch (or a multi-select) is established, one talkgroup becomes the "supergroup" and is the talkgroup that will show as active on a scanner. Patching (and multi-selecting) is transparent to the subscriber radio users (aka troopers).
You might want to check how your radio handles patching. Most "modern" scanners support it - meaning, if Anderson and Greenville dispatch groups are patched together and Greenville is the "supergroup", if you have both talkgroups programmed and not locked out, your radio will typically show activity on the Greenville talkgroup. If you have the Anderson dispatch group enabled, but Greenville locked out, you still should hear the traffic on the Anderson group. On my GRE/RadioShack scanners, I see a "ptch" displayed when this happens.
If you have this feature disabled on your radio, or your radio doesn't support it, this could be why you're missing traffic. Trying programming and unlocking all SCHP troop 3 dispatch groups, and listen closely to see if you hear calls dispatched for the Anderson area on either the Greenville or Pickens/Oconee groups.