Jimmy had been watching these two people closely; for them to be conducting surveillance here, they must not be anything major figures. It's even possible they're simply hired to monitor for a few days without knowing who's pulling the strings.
After making a phone call, the two continued to wait in the room as the people upstairs kept observing from the window.
A mistake was made; Pam should have turned on the light when leaving the house. It wouldn't use much electricity, but at least it could delay them a bit longer. Now they've just returned to the surveillance point and spotted something unusual.
If the delay could have continued, it might have offered the chance to follow them to their hideout. But once they returned and detected something off, chances are they'll contact their superiors and be extra cautious, which makes it unlikely they'll go back to their hideout.
