I don't think you should borrow something then use it for something it was not intended for,
he should have asked you if he could pry with "your" blade.
Some fixed blades can be used as a pry bar (like Busse) but a folder isn't the best tool to pry with

Pretty disrespectful and dense boss, I think this falls into the "you break it, you replace it" category,
especially after he saw the damage he did