But do some Sanskrit versions still exist and are they accessible? Or is the Vinaya now only in Chinese, Tibetan, and Japanese (and perhaps Mongolian from before 1936).
One thing to first note here is that the Sanskrit might have been written down after the Chinese in some cases. I know that might sound odd, but when Faxian went to India in the 5th century he noted the following:
"I originally went seeking the vinaya, but in the countries of northern India all the masters transmit it orally without an original that could be copied."
Faxian was quite original and progressive as he might have been one of the first people, and a foreigner at that, to copy down the Vinaya which he brought back to China (or at least tried to as it was apparently lost at sea).
In any case, it is misleading to assume every Chinese text was translated from Sanskrit. In reality the earlier scriptures such as the vinaya (all of which were translated into Chinese in the 5th century), if translated directly from other languages on paper rather than orally, were probably using languages like Ghandhari or other "dialects". The problem is that the Chinese just called every language or script from India fan2
梵, so we have to make educated guesses often at what language they were translating from.
In any case, we have Sanskrit texts. If you look at University of the West's Buddhist Sanskrit archive they have a few texts digitalized (under the sutra heading):http://www.uwest.edu/sanskritcanon/dp/i ... q=node/108
So, in short, yes we have the texts, but unfortunately there isn't a lot of interest in studying them. This is unfortunate because the Vinaya was probably more influential than most of the texts people read now in English. Every single bhiksu(ni) from Buddha's time until the present has read or studied some version of vinaya. They might not have memorized their particular version of it or even abided entirely by it, but nevertheless they all had/have to study it to some extent.