Thanks for the great replies, everyone!
I'm not giving up for good, but just wasn't willing to get up in the middle of the night to take everything apart and dry it out after the water went everywhere.
I was afraid that I had ruined it and wasn't looking forward to telling the home health company that I ruined it after one night! Luckily, everything worked once I dried it out.
Amandasgramma, thanks so much for the info about the water pillow. I'm a stomach sleeper too, so that's so good to know!