@dangillmor
There are no "correct" uses of words like "lose" and "wealth" here, that make it "innumerate" or otherwise wrong to say that he lost $200 billion.
No one thinks that he had that much in a bank vault in cash, and had to give it back. :)
It's entirely reasonable to describe a $N drop in "theoretical wealth" as "losing $N".
I don't really understand the vehemence that some people put into this kind of claim. (Except when they say that some billionaire isn't "really rich" because their wealth is mostly in stock. I gather you aren't doing that here.)