How to unhide 'Very Hidden' Worksheet

You do it like this:

1. Open VBA editor (Alt+F11)
2. Open the VBAProject corresponding to your file.
3. Open the "Microsoft Excel-objects" folder
4. Select the Sheet you've hidden.
5. Go to the properties (press F4)
6. Change the property "Visible" to xlSheetVisible instead of xlSheetVeryHidden

One option is to do it with VBA

Try out the below:

Sub UnHide()
Dim ws As Worksheet
For Each ws In Sheets
    ws.Visible = True
Next
End Sub

This will show up ALL sheets that are hidden, or very hidden

In VBA editor, go to the sheet properties and change the below property