I want to understand this, because if my current understanding is correct, there might be a faster way for you to get to your call.

When you say locked, do you mean screen lock or device lock? I get the feeling you mean screen lock (no pass key needed), and not device lock (pass key needed), true?

If the above is true, it seems you're using the power button (on top between +/- and IR port) to unlock the screen. If so, maybe try using the screen lock/unlock slider (on the side with headphone jack) or try opening the keyboard. Both of these methods unlock the screen instantly, no on-screen sliding necessary.

If I'm way off here, sorry for the post.