50 years after the event, Dr. Harry Binswanger has decided to reveal the identities of all of the workshop participants named in the appendix to the second edition of Introduction to Objectivist Epistemology. This has been a mystery for quite some time!
I'll quote the key section, and you can visit Dr. Binswanger's public blog to see the rest:
https://www.hbletter.com/objectivist-workshop-participants-identified/