This “event” very likely refers to when Flynn spoke at the Cambridge Intelligence Seminar in Feb 2014, and the suspicious Russian-linked person supposedly in the cab was @RealSLokhova (who also attended, and briefly spoke to Flynn)

(Most of that’s still redacted as well) pic.twitter.com/d7fCF2dGas

— Undercover Huber (@JohnWHuber) May 3, 2020

.....