BioShock 2's first batch of DLC, the Sinclair Solutions pack, may have been on the game disc all along.
Users on the 2K forum (spotted by VG247) recorded the download size as a teensy 24K on PC and 108K on Xbox 360. That's what it says on the Xbox Live Marketplace page too.
Developer 2K Marin would need something akin to a miracle to squash all of the Sinclair Solutions content - two new playable characters, 20 new trials, a third weapon upgrade for each weapon, five additional masks, rank upgrade to 50 - into such tiny files.
2K Games is avoiding comment at the moment, which suggests that a more measured and senior statement be needed.