humbaba
sleeping until $7000
You have just discovered why margin calls exist. Briefly, your broker requires that you maintain something like 125% of the short in your account. This way, even if the stock goes up sharply, there's enough to cover your short. If the short value gets too close to your margin the broker says, "add more, or we close your position." Depending on broker, yada yada, you get some time to add funds (or cover of your own accord).If short, and you can't buy to close due to insufficient funds... what happens?
However, if you've been called and your short interest gets too close to the margin the broker will just cover for you.
I'm not trader, etc., so take it with a grain of salt, but I think the sharp rise today was from exactly that. I think with the recent rises many (retail) shorts had been margin called. Those who were strapped were hoping for a drop and neither closed nor added money. Once the run started brokers were busy closing positions which added fuel.
Do I think any big short closed out? Possible, but I wouldn't attribute the sharp rise to that. They don't have a time crunch and don't have to cover going into a rise. That said, I do think there has likely been some covering. I think the upcoming short interest numbers will show an increase due to their age, but I think the one after will show a drop.