This is not true. SVB had 91 billion in hold-to-maturity securities. These were auctioned off to other Banks. The FED did not take them.

If the Fed did take them, it would be a drop in the ocean. The FED is already holding 2.7 trillion dollars of underwater mortgage-backed securities they bought.

They have six trillion dollars of other securities they are holding.

Nobody can do a bank run on the Fed and they control the interest rate, so despite their colossal unrealized losses, they can wait it out.