Transwarp is ten thousand times faster than Voyagers fastest ordinary warp speed.
Transwarp navigation sensors are comparable to the speeds Borg Cubes travel at, which means that they know where everything in the galaxy is and what sort of threat it poses to the Borg as an empire and as Sunday drivers. Everything can be tagged and tracked so it probably is tagged and tracked. Even if Voyager could hide for a little while, as soon as they stop hiding, the Borg know where they are instantly and can head them off instantly.
The Only reason that the Borg were not harassing Voyager constantly like the Kazon or the Hazari in Think Tank, is because the Borg did not give a damn.
Cost has to equal benefit.
The cost of recovering that ordinary Drone exceeds the benefit of recovering that ordinary Drone, until the fricking Queen sent for Seven a year and a half after she ran. Not an autonomic collection agency or Anika's immediate superior (look at me thinking in human terms of hierarchy), or even the entire collective itself. The Queen's ideology is seemingly independent of typical Borg protocol, almost as if she's in charge of "special projects" and Seven was worth their while as a special project, but not as an ordinary Drone.
The Borg were good with where Seven was (90 percent of the time.).
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