What "wild card open" would do for you is allow you to hear any talkgroup that's in use on the system (and not specifically locked out by your programming). For example, say you've got your scanner programmed with these:
TG Name
32 PD Dispatch
64 FD Dispatch
128 Animal Control (locked out)
You also have it "wild card open". A transmission on TG 32 comes in and you're scanner will say "PD Dispatch". A transmission on TG 128 comes in and your scanner will ignore it. A transmission comes in on TG 178 (one you don't have programmed in so the wild card takes over) and your scanner will say TG 178, but you'll still hear the transmission. You'll now know that TG 178 is in use and hopefully from hearing it over time you'll be able to identify what it's used for (and submit it to RR with how what you've identified it most likely being called).
While you may not be 100% accurate, you can probably make a pretty good guess on what it is. Now if you're lucky, you'll hear officers on the dispatch say "car 54, meet me on OPS2" and next hear them on that new talkgroup, so you can be pretty sure that the talkgroup is "OPS2". It may be that all you can tell is that it's used by the city's water department, so you would report it that way.
If you're having difficulty telling what it is, post it to that state's forum (or whatever forum would be most appropriate) and state that you've heard transmissions on that new talkgroup and ask for others to monitor it to help identify what it is. Since the RR database is created by folks submitting what they've heard and identified (no, the systems generally don't send RR an e-mail or otherwise notify RR with changes they've made on their systems), this is how the database is kept current.
