Putting on something from your superior is already a stupid idea, but taking Ghost's mask and putting it on was probably the stupidest thing you could have done. But it was so tempting, he wasn't there and the mask was just lying on the table. Plus, she smelled like Ghost and that gave your fantasies free rein, meaning you didn't even notice the door opening...

"Seems like I have to teach you not to take other people's things, don't I, doll?"