Can you tell me exactly what field you were trying to edit?
I found it was on it's own layer - so I just deleted this layer. But if there's an actual way to edit - I'd love to know!
How well do you know InDesign? You can edit anything in the template you want. But you need to understand where it is located: layer, Parent pages (formerly Master pages), what type it is: text, variable, graphics, and if it is locked either on an individual basis or per layer.
The screenshot provided lets me guess, that it is on a parent page.
This would not be a "stock issue" but a question to ask in the InDesign forum.