Doesn't work with BitLocker and a TPM chip. The key is kept in protected memory on the chip and only authenticated code can use it.
I don't think that's true. The passphrase (perhaps hashed?) pay only be in the TPM chip, but the actual cryto key used to decrypt disk sectors is in main memory, because the main CPU is used to do the decryption. There's nowhere near enough bandwidth to and from the TPM chip to let it do the actual disk encryption/decryption. There's not even enough bandwidth to ask the TPM for the key each time you want to do a disk transfer, and erase it from memory after the disk transfer is completed.
This means that software that extracts the encryption key from memory probably can't turn it back into the passphrase that the user enters, but if you have a copy of the disk and the key, you don't actually need that passphrase.
The TPM is not a high-performance device and doesn't do anything but give out the keys on (authenticated) request. What the software does with those keys is up to the software. If someone has privileged or physical access to the machine while the keys are in use, all bets are off.