Interesting article, seems to be similar to a hardware keylogger though.
As the record is stored on the disk itself, the attacker would need access to the machine again or did I miss something (as (automatic) transmission through network is not available yet)?

Yes, it does require access a second time.

According to a Bruce Shneier and a commenter on his blog:

"Actually Bitlocker is the only Microsoft product that does support Trusted Computing, and thus (if configured that way) will prevent exactly that attack (different bootloader = TPM won't release the Key).
And what used to be called Palladium is going much further than TPMs, it more corresponds to, for example, Intel Trusted Execution Technology."

So when the victim returns to use the laptop it won't boot since the bootloader has been modified. A clear indication that it has been tampered with.

The problem is BitLocker doesn't natively support pre-boot authentication so without a 3rd-party plug-in KonBoot would work fine.

That is extremely suprising to me.