It's in the OED (which isn't free, but my whole county has access through our library system) under Limited's spelling (my guess would be that "vagitis" is a typo). It's obviously not a popular word, but it hasn't fallen out of usage completely. It's a shame I was gone for this one. I think I'd have guessed the right answer, although I don't know that I'd have come up with something that would have fooled anyone else...
Dictionary.com sucks, although I did check Merriam-Webster and they don't have it either, so you do need a good dictionary to find "vagitus."