If you have accidentally deleted a session, the OKRs of this session are not lost and you can retrieve them. When you delete a session, its OKRs are stored in Objectives without sessions section.
To access the OKRs of a deleted session, perform the following:
In the navigation pane, under OKRs, click All sessions.
At the end of the lists of all sessions, click Objectives without sessions.
You can edit the objectives individually or use bulk operations.