Hi Kim
There should still be an Alert appearing in the managers Dashboard - if they have the default Alerts block showing.
When the new plan approval request link is checked the declined learning Plan will show and there there will be an opportunity to approve the plan. The Site admin can also do this by browsing users and clicking on the appropriate user and Learning Plan an Approve this.
If the manager has accidentally deleted the staff objective in the Learning plan then the user can add the Objective again.
Regards