Sheet appears as Workbook - cant delete worksheet

[blackduck]

When in VBE, I have a worksheet that shows up like "ThisWorkbook" (as well as having the usual 'ThisWorkbook').

Does anyone know how I would have got this there, and how I can delete it?

thanks
hopefully

 

[combo]

Is 'ThisWorkbook' a code name or sheet name (shown in braces in 'project explorer' window)? For me excel will not allow to have two the same code names (for workbook and worksheet).
How do you try to delete the sheet - by code or UI? Is the workbook protected (structure)?

combo

 

[blackduck]

In the VBE window it is just Sheet7. There is no name after it like eg. Sheet6(Planner). In the properties window it has all the same sort of attributes as 'ThisWorkbook' and in the name field of the properties (name) ThisWorkbook.

I have tried to delete it via the UI. If you go back to excel the sheet is not visible.