Happened to me yesterday. Checked the battery stats. Facebook and Facebook messenger drained 19% of the battery a peice. Never even had them opened. Deleted last night and today my battery is still at 90% 8 hours after I took it off the charger.. No more fb or fb messenger for me for awhile..
What battery stats did you check to determine that FB was the culprit? I too experience higher than usual battery drain this morning, but non of the battery stats had FB as the culprit. Uninstalled FB and battery does not seem to be draining as fast now.