Just keep your radio on ID search. Another thing to consider is that the talkgroup may not be active on the GFW site because there's nobody using that site who is tuned in to that talkgroup. That may sound a little circular, but let me explain.
Trunk systems, particularly wide-area ones with multiple sites like Newfoundland's P25 system, have to manage their resources carefully. You can't have dozens of talkgroups active on every site, because it would cause every frequency to be in use constantly, wearing out the equipment, and to boot, it would be a waste because for example nobody in Clarenville is interested in hearing what's going on in GFW. The way they make the system most efficient is by making sure the talkgroups are only sent to tower sites where there is a radio that is tuned in to them. So, an officer with a radio set to Springdale's talkgroup could start out on the Springdale tower site, then have to run in to GFW for an errand. Once the signal for the GFW site gets stronger than the Springdale site, his radio would switch over to GFW, and tell the system to bring the Springdale talkgroup over there for him. Once he leaves the coverage area of the GFW site, either by moving even further down the road toward Deer Lake, or by going home to Springdale, or even just switching off his radio, the system no longer has a reason to carry the Springdale talkgroup on the GFW tower, so you (as a scanner user) will no longer hear it.
How do you solve this in the Home Patrol? It gets tricky, and may not be ideal (you may not be able to pick up the signal well, or at all) - plus you run the risk of not hearing comms for other areas (like GFW). But you can listen to one specific tower.
When the scanner is on the P25 system (showing it in the top bar), tap that bar to hold on the system (the bar will turn yellow). Tap the right edge and then hit "Advanced", then "Site Information" on the screen that pops up. You'll see a list of sites, many of which are probably highlighted red. Those are automatically locked-out by the scanner based on your GPS settings or postal code input. On any of the black-background sites EXCEPT Springdale, you want to lock them out. Tap on the site name, tap Avoid Site, then OK, then Back. Scroll down (use the arrows in the lower right) and do this for all the black-backgrounded sites EXCEPT Springdale. Then hit Listen.
As I said, depending on your location, you may not even pick up the Springdale tower. You'll know if you are or not by whether or not the white signal-strength bars in the upper right corner flicker on/off when the scanner passes over the P25 system (since the scanner will only be searching for the Springdale site).
