This is an odd one and I don't know if there are many posters out there who have the answer, but if any group of guys know the answer you do.
My neighbor was zipping through the channels on his Philips TV and somehow got into a service menu where, to the best of my guess, he changed the firmware ID for his TV. He now has a different menu and has lost one of his AV inputs. As well, he has a listing for a Front AV input that is not even there.
I know how to get into the Philips menu on their DVD players so I am guessing that there might be a source for similar info on their TVs. Even just learning the correct terms for what he accessed might help.