Well I was hoping days or longer… ‘we’ve traced the rebel spies’ sounds like a long process not just glancing out at the corvette’s license plate. Comments floating around make it sound like the latter though. I will see how this all holds up on second viewing.
Princess Leia Organa: [smirking] Darth Vader. Only you could be so bold. The Imperial Senate will not stand for this. When they hear you’ve attacked a diplomatic–
Darth Vader: Don’t act so surprised, Your Highness. You weren’t on any mercy mission this time. Several transmissions were beamed to this ship by Rebel spies. I want to know what happened to the plans they sent you.
Princess Leia Organa: I don’t know what you’re talking about. I am a member of the Imperial Senate on a diplomatic mission to Alderaan–
Darth Vader: You are a part of the Rebel Alliance and a traitor! [to the Stormtroopers] Take her away!
[Leia is taken away]
Imperial Officer: [to Vader] Holding her is dangerous. If word of this gets out, it could generate sympathy for the rebellion in the Senate.
Darth Vader: I have traced the Rebel spies to her. Now she is my only link to finding their secret base.
Imperial Officer: She’ll die before she’ll tell you anything.
Darth Vader: Leave that to me.
I think the full context of the conversation Vader has with Leia - and then the Imperial Officer - may be of use. There is a fair bit of exposition in there.
For me the ‘traced’ line doesn’t seem to indicate a long process (unless taken as referring to his overall mission to destroy the Rebellion which could well have been ongoing for some time) - more of that she is the latest, and now only, link in a chain to him finding that Rebel base - especially the ‘Now she is my only…’ part of the line.
just my two penneth on it.