When you click DISABLE or DELETE practice from Practice Manager, it goes into a "DISABLED" state (prac_status=1), and shows in the bottom of all drop down selections. But does not show in typed in search boxes. You can select it from Practice Manager, and re-enable the practice.

After a period of time (this is configurable by organization), which is by default 6 months, will vanish from the dropdown list. (prac_status=2). This is the hidden disabled level. You can not re-enable the practice from the CC application, you'll need to contact support, and we'll re-enable it in the database.