I'm actually surprised that any Palazzos came with a "U" shaped dinette, but your's certainly did...
http://www.coltonrv.com/wp-content/u...ure-Colton.pdf
For most of us with a booth dinette, the extra cushion is usually found under the bed storage... but, if the former owner removed theirs and put it in storage at their home to make more room in the coach, it may have never got back....
I have two 'extra' Cushions, myself.. one was from a former Georgetown, which we traded in, but forgot that our extra cushion was still at home, and another 'extra' cushion for our Palazzo that we've never used - it's somewhere at the house, too.
I'm surprised that you're trying to even use the U-booth for 'sleeping'... would it even be long enough for anyone? : /
I'm always amazed at the number of 'beds' or 'sleeping areas' that manufacturer's tought for their coaches - a booth that is 48" long is hardly considered a 'sleeping option', unless you're an infant, or 3 year old. That's like saying a twin mattress sleeps 'two'. : /