I have no volume on ONE channel the rest of the channels are fine. What button did I press that I shouldn't have?

Doesn't sound like its qanything you pressed... the volume control has no idea what channel its on... and I've never seen a TV that lets you mute one channel and not the others.. or where volume was adjustible by the channel.

Unless you somehow managed to tune that individual channel off center and almost to the point of losing it... I can think of anything you could have done to cause this... and I've a Degreed engineer and 52 and have seen a LOT of tvs over the years.