Actually those funds were deposited on MtGox by Patrick Murck, cf:

MtGox officially confirms currently having on deposit those 15,006.00000000 BTC. As you may know, our system uses a pooled Bitcoin online reserve, which means that activity beyond that point is no longer from Bitcoinica, LP.

We also have disabled the ability to withdraw Bitcoins from the account where those Bitcoins are held to ensure the security of those coins until we receive validated information from an appointed receiver for Bitcoinica, LP.