re: Say your brokerage collapses, you still have your stock right?

The brokerage owns the securities you own in a margin account.

I personally use a cash account at Schwab so that they cannot loan out my securities.

This is why you have to have a margin account in order to short individual stock(s).

Margin accounts are rehypothecated over and over just as the banking system itself is. Rehypothecation itself is one of the reasons why there has been a severe shortage of good collateral leading to trillions in reverse repos overnight.

If the system itself was true and transparent, the risks wouldn’t be near as great.

Here is more on rehypothecation from the IMF:

LINK