This implies that Obi-Wan still has the receiver for his listening device (planted back in strip #288), of course. He probably still has his underwater oxygen extraction apparatus too.

Player characters never get rid of equipment that might come in handy in the future. Once it's on your character sheet, don't let the GM take it away from you without a good reason.

Transcript

Obi-Wan: Hang on. How can I hear Jango and Boba?
[SFX]: Ryyaarrrk! {the acklay screeches as Obi-Wan fights it with a spear taken off a guard}
GM: Jango's still carrying your listening device. He wants you to hear it.
Obi-Wan: But that means I should have heard everything he's said since the asteroid field.
[SFX]: Ryyaarrrk!
GM: Okay, no problem.
{sepia flashback to the asteroid field}
Jango Fett: That EMP device should get him off our tail for long enough.
Jango Fett: We have important business with the Trade Federation. They're bringing in that loser Dookû and the Separatists.
Jango Fett: If we play our cards right, we'll have all the factions working for us, without them knowing it.
Boba Fett: Can I have a clone army too?
Jango Fett: We'll see. But it's not easy to trust even yourself. You have to know yourself first.
Jango Fett: When your mother got divorced, I realised oaths are insufficiently binding. I built a failsafe into the—
Obi-Wan: {ending the flashback} Oh look, don't bother.
[SFX]: Ryyaarrrk!