Partition gone and I am really worried

I first got my friend to install bootcamp on my laptop. It worked fine and all, but I just didn't use it often so I decided to delete it. I used the bootcamp assistant program and deleted the partition. I then wanted to get the 180 gb from the windows partition back, but when I looked in the disk utility, all that wad there was the 320 gb. I then erased the disk and am attempting to reinstall OS X and I'm just really scared now and need some input.