Plot hole in Watch_Dogs - did I miss something? (Possible Spoilers)

I'm enjoying Watch_Dogs and the main story picked up a bit after the first few missions.

Anyway, I'm now in Act IV and I can't help wondering if I missed something in a previous act.

Early on in the game, the main antagonist, Damien, kidnaps Aidan's sister. Aidan spends most of the rest of the game brutally slaughtering various gang members in order to get her back. Not only that, he traces phone-calls and hunts people down via the ctOS network on several occasions throughout the main campaign and in various side missions.

Did I miss something here? Why doesn't Aidan simply

Trace Damien's calls in the same way and hunt down the location he's holding his sister? He handled an entire apartment block full of Iraq's goons with relative ease and from what I can gather, Damien does not have anywhere near as many resources as Iraq (at least in the early game).

Does this get explained anywhere, or are we left to simply make assumptions that, for example

Aidan is worried if he makes a direct attack, Damien will simply kill his sister?

If that's the case, why, at the beginning of Act IV, does Aidan

Call Damien's bluff by telling him to kill his sister? Surely if he thought Damien was bluffing, he would have made a positive move against Damien to retrieve her, rather than the passive move he made.