The unexpected communication with the major bad guy is a trope* that can be used to good effect in a game. It happened in The Lord of the Rings, when Pippin grabbed the Palantír and copped an eyeful of Sauron to the face. You can also arrange it through various other means, such as the crossed telephone line, a mental intrusion during a cyberspace net-run, or even bumping into each other face-to-face while walking on the street of a busy city. Thrown into such a situation unexpectedly, the heroes will need to scramble to (a) avoid giving anything away, (b) try to extract anything useful about the bad guy or his plans out of the connection. And of there's the added bonus of causing a moment of panic, which is always good value.
* As far as we can tell, it's not a Trope, listed in TV Tropes. The closest thing we could find is Surveillance as the Plot Demands.
EDIT: Almost exactly a year after this strip was first published, TV Tropes added Butt-Dialing Mordor, which is precisely what we're talking about. (And of course it includes this strip as a prime example.)
Yoda: No, it wasn't metaphysical, and no, you failed the test.
Luke: But it was my own face! That's like Metaphor 101!
Yoda: Naïve, you are.
Luke: Look, I know where my face is, and I'm pretty sure it stayed there the whole time.
Yoda: Yes, yes, reverted to metaphor the midi-chlorians did, once you severed the psychic connection.
Luke: Psychic connection?
Yoda: An avatar of this Vader person you summoned, from your fears.
Yoda: My fault this is. Partly. A small part. Underestimated your power, I did.
Yoda: Vader heard, Vader saw, Vader felt your sword blows.
Luke: So, did I kill him?
Yoda: I believe not.
Luke: So, if he hit me I wouldn't have died?
Yoda: Let's say... no.
Luke: No I wouldn't have, or no I would have?
Yoda: Okay, next test!