If def from multiple players got sent back, and there is only 1 sitter active on the account that you trust, an explanation could be that account owner Mary Jane(or dual) sent back a portion because he/she couldn't handle the big amounts of def. It happens often, people panic. And afterwards they say that didn't happen because they don't want to look bad.
Or in hindsight hoping to be top defender alone. You never know. But I'm rather sure admins wouldn't remove def or make it vanish. There is a solution to this that's probably not as mysterious as you'd think