LOL, I had a friend who did that once and she had kept the pieces so long that she swore up and down that they were hers that I was forced to prove they were originally mine with photographic evidence. I was ok with her keeping them though as they suited her more than me anyway and I had only brought it up jokingly. She was properly apologetic afterwards and kept asking her if she had anything of mine every so often that it kind of became a joke between us.
I never let anyone borrow shit
Im stingy like that