I was told by the immigration official that these forms are no longer needed - they have been replaced by an electronic record (as the I94W green forms were a few years ago).
You can get your admission number from a CBP website:
http://www.cbp.gov/i94
This was announced on the very same CBP website you refer to more than 10 weeks ago. The system has been in operation for two months now.
http://www.cbp.gov/xp/cgov/travel/id...94_rollout.xml