ipod touch 4G with horizontal white line

Hello, I have a brand new ipod touch 4G. Two days after getting it I was in the middle of looking at some apps and a white line across the screen appeared (horizontal line). I turned off the ipod several time with no change. After looking up what is may be I found it was most likely a bad pixel and there was nothing I could do. I called apple and set up a repair which was about as easy as it could be. The next morning when I got the pod out to take it to UPS, the line was gone. What the heck is going on?