Let’s get something out of the way right now: It’s ridiculous to think that Ichabod didn’t grab a single thing from the fenestella before setting the charge to destroy it in “What Lies Beneath.” The underground chamber, built by Ichabod’s former BFF Thomas Jefferson beneath the tunnels that already ran under Sleepy Hollow, contained years worth of research pertaining to Ichabod and Abbie’s roles as Witnesses in the apocalypse. There were books upon books of knowledge contained within its walls and now they’re lost for reasons that I understand but don’t accept or even recognize as being valid.
The fact that Ichabod and Abbie chose to save the two remaining members of the survey team (R.I.P. Other Guy) who were trapped in a cave below even that chamber made sense based on what we know about them as a team. Ike and Abbie are heroes who risk their lives on a daily basis to ensure the safety of human beings everywhere, but the stakes that should have accompanied their choice to save the two men but lose all of that important research simply didn’t exist.