I think you're looking for the word "trunked system." A trunked system has "talkgroups" within it which is sometimes referred to as "channels." You might also be talking about an agency that may theoretically use 10 talkgroups, but you only have 6 of those talkgroups programmed. A scanner is not smart enough to know what agencies use what talkgroups and is only a level of understandings that humans have. A wildcard will (attempt) to give you all the talkgroups active on the trunked system not limited to agency and will include anything that is part of the system which may include the county. I believe way you can use a wildcard search to find unknown talkgroups is to program every known talkgroup into you scanner and then locking out all those talkgroups. This should allow you to find new talkgroups if they exist.