Kira's done that a couple of times before, and yes I think it is when she's hungry. If there is more than 12 or so hours between feedings, I can hear Kira's tummy making hungry noises and she will sometimes ask to go outside so she can eat some grass while I get her brekky ready. I don't really get to sleep in anymore now I have a toddler
but when we did sleep in on a weekend is when Kira would do the hungry-puke. If I was planning a sleep in, I'd give her a couple of bikkies just before bed and that solved the problem.