Hmmm. Sounds like it is more of a mental habit than a physiological need -- but the mind is a powerful thing!
I used to have a snack every day after getting home from work. Since going primal and shifting my eating schedule later in the day, I don't need that snack anymore. I'm not hungry. BUT, it took me a couple months of self-talk and intentional distraction to convince my body not to *feel* hungry because my brain said "Oh, look, it's time to eat!"
Working out is the ideal hunger (or fake hunger) elimination strategy for me. That might not work for you in the middle of the night, though!
How about some other kind of mouth-distraction, like a cup of tea?
Or maybe a non-food distraction, like soduku or a good book? Perhaps reading books like Protein Power, The Primal Blueprint, etc would be helpful not only as a distraction, but as a constant reminder of why you've made this dietary choice.
You could try a different eating schedule (maybe go a week or two without IF-ing) and see how you do. If it doesn't work and you find that you prefer the IF schedule, you can always go back to it later.