You could find your "inactive" items by doing the following:
Open the drop-down at the top right corner
Check off the "Active" line to add the column
Find the "Active" column to the left of your screen
Open the filter and check off "All"
Now you should be able to find that SKU.
When you find that item, you can manually reactivate it by opening the below dropdown menu, and clicking "Activate"
