I've thought about something like that. Honestly, I had a sit pad I could've used, and I could've adjusted my clothing too - I was DEAD asleep, though. I didn't notice my feet were ice 'till I woke up Sunday morning.
The weird part about it was that I (my WHOLE body) was TOASTY until I got up for a pee break around 3am. Turned out that NCPatrick was up too, and we talked for about 45 minutes before I went back to bed - just enough time for my feet to get cold. I figured they'd warm up after laying in the hammock for a while, but I guess they never did. I'm not sure exactly what caused it.
It's hard to even compare to the previous night, because I tossed a heat pack in my footbox Friday night before I went to sleep, being overly cautious about the fairly bad circulation I have in my feet.