Fighting

So Jennifer leaves her scrubs at the store one day after work. The day that it happens, I told her to take it home cause I don't want her leaving her shit like that at the store. A week or so passes and she goes looking through her scrubs and can't find something in her scrubs. What you ask is she missing??? Money....an ID.....nope a pen!!!! She blows up at me over a freaking pen missing and that I don't care about her things and I should take better care of those things. But it's a pen, that's all. Not a super special pen, no it's just a pen. Seems like a good reason to fight if you ask me.