Excel 2007 : Drawing Toolbar Disabled

Edit: I've found the solution. When attempting to add rows elsewhere in the workbook, I kept receiving the error "Cannot shift objects off sheet". As I researched that, I discovered that the solution in Office 2007 is to show objects, which had somehow been disabled in this workbook (likely by shortcut CTRL + 6). Flipped the switch, everything is back to normal.

A workbook I'm editing used to have a drawn image on one tab, which was linked to a macro for ease of use. Another user had been in charge of the workbook for a time, and as I'm accessing it now, I see that the macro button is gone.

I'd like to draw a new one and re-link it, but my drawing tools are apparently unavailable. I've tried opening this workbook in Excel 2003 as well, and the tools are still disabled.

I've tried changing the sharing permissions already (it was already turned off, I turned it on and then off again, nothing changed), and the worksheet security properties (the sheet should be unlocked for editing, including adding images).

Is there something I'm missing? It's not critical that I add this shape, but the question as to why I can't is starting to nag me... Any help is appreciated.

Thanks!