Reverting References
The Revert Reference command undoes (reverts) all changes made to a reference since it was last opened or saved. Revert Reference is not available after you close the reference.
To revert changes, Control+click in the Edit panel, then select Revert Reference from the list.
To remove the very last change made to a reference, use the Undo Typing (⌘+Z) command in the Edit menu before closing or saving a reference.