Sidewise should have its own 'Recently Closed Tabs' list. That way, an accidentally closed hibernated tab/tree can be recovered with ease.
When restoring, the tab/tree should be restored to the position and state it was in before (if that position is still available; otherwise, nearest location will do).
I sometimes accidentally close hibernated tabs which I haven't opened for a long time. Then I can't Ctrl+Shift+T to restore them.
Customer support service by UserEcho