This happened to me yesterday as well. EWR-SFO, scanned at the gate to board, and while waiting to depart, everything disappeared. The flight was oversold, so I was scared that I was about to ride into battle with the GA armed only with an e-ticket receipt from my email. Luckily that never materialized, but I still thought it was odd that everything (BP and Reservation) vanished from the app.

Perhaps it's a bug in the latest update?