Once you mark and “Opportunity” as “Won,” it becomes a “Job” so it will no longer be visible on the Opportunity list.  In other words, it is no longer potential business (an “Opportunity”) but rather current or future business (a “Job”).

mark as won

On the “Job List” tab of the Sidekick, check the “Jobs” checkbox to show your jobs. Click both the “Opportunities” and “Jobs” checkboxes to see both displayed in the same list.

show in sidekick

Or go to the “Ordering” button at the top of the page and select “Jobs.”

ordering job