I doubt 5 million odd warrants....and only 2.5 million odd not in the hands of Hepa/Eastern, I don't think there's sufficient liquidity there that RVX.WT would be available to short.  Here's an article explaing why shorting warrants isn't a good idea:  

http://www.stockwarrantshq.com/2014/06/11/shorting-warrants-cool-dont-do-it/

Note what it says right off the bat:  

Should you ever short warrants? The short answer (get it, the short answer) is NO. It’s simply a way to turn a safe trade, shorting common and being long warrants, into a nightmare

I just pulled this article up.....but that's what I've been suggesting has been going on....that its those who are behind the 800 odd thousand short, that they're the ones (by and large imo) buying the warrants....