Grayson is just being an ignorant fool. There is an enormous swaps market between banks and central banks all the time. Asking who ended up with the cash is like asking who ended up with the share of IBM you just sold in the market.
The fed exchanged dollars for bonds in a standard transaction that goes on every day. It was to ease the acute lockup of the credit markets and prevent the collapse of euro area banks. Most of it went to the ECB and is fully collateralized. Riskless transactions with other central banks.
I love watching Bernake tremble with fear but sometimes these grandstanding scenes just make these congressmen look dumb.