Have you tried switching the tv off for a while then switching it on a bit later?. How many hours did you leave the channel on for?
If it has been left on for a long time, and switching it off for a while then on again does not remove it, then I'm afraid it will be permanent. Burn in is actually when the phosphors on the screen become damaged (for plasma and crt). This is most likely to happen when the tv is new and hasn't been used for very long (say 200 hours). Also having high contrast and brightness settings will make it occur more readily. And of course leaving it on a picture with a static image for a long time.
Newer plasma screens are much more resistant to the burn in problem depending on the make as they have been made to display static images as if the screen is moving the logo about slighty - just to an amount so that the viewer does not notice it.