If you inactivate a piece of equipment, and there are active Schedules associated with that equipment, the Schedules themselves remain active. The way to find any Schedules without pieces of equipment tied to them is to set your filter options to view "Empty (No Machines)".
If a Schedule is tied to a Machine, and the Machine is inactivated at some point, and then activated again, that former association between the Machine and any Schedule(s) is not automatically restored. You will still be able to see the Schedule, but you will have to re-associate the equipment (machine, asset) with the Schedule.
Best Practice Pro Tip: For the reasons stated above, before anyone ever inactivates equipment or machines, we strongly recommend that you first look to see if there are active Schedules tied to that machine before inactivating any equipment.