I've had that before. It's really only happened to me when I was having issues with heartburn. Contrary to what people say, I'm the type of person that can drink a glass of milk to cure my heartburn (usually). So, when that empty pit feeling of hunger arose, when I knew I wasn't hungry, I'd chug a glass of milk. I could feel the milk coat everything as it went down. As soon as it hit my stomach that feeling would leave me. It may sound odd, but that's what worked for me.
I know lots of people can't have milk... And maybe were not even experiencing the same feeling.
How long does it take for your stomach to stop feeling this way? Usually it takes the brain like 20 minutes to register that it has food in it.