All you've done is accidentally zoomed everything out. Firstly try going to 'View' and then 'Windows Layout' and choose 'Default Layout' that might put everything back to normal. If it doesn't fear not, just hover over each track box and make them larger by dragging it down.

If you can't figure out how to do that you can reset your Sony Vegas back to it's factory setting. Close Sony Vegas, go to 'Start' press CTRL + ALT + SHIFT keeping it held down and click on Sony Vegas. Don't let go until a whit box appears, if Sony Vegas loads up instead of the white box, you've done it wrong. Anyway back to the white box, tick the white box and press OK, Sony Vegas will load up as if did when you first installed it. (Don't worry it won't change any of your projects.)

Im sorry, are you saying that you clicked on something twice and deleted/muted your audio track?

sounds , cut..... I just clicked 2 times on somethink but I forgot on what.