When property is entrusted to a person he is responsible for it, and if that is the case then he is obliged to protect it, because Allaah says (interpretation of the meaning): 

“Verily, Allaah commands that you should render back the trusts to those, to whom they are due”

[al-Nisa’ 4:58]

Part of rendering back the trust is taking care of it; he must take care of it by putting it away in a suitable place. 

If he takes care of it by putting it away in a suitable place, and he is not negligent by either doing things that are not permitted or failing to do what he should, in this case he is not obliged to do anything. 

But if he is negligent and does not take care of it by putting it away in a suitable place, or he is negligent by putting it in a place where it will not be safe when he is able to put it in a safe place, or he disposes of it, or he uses it himself and so on, then after that it is stolen, then he is responsible for it. The guideline concerning that is negligence; if he is not negligent (and it is lost) then he is not responsible for it.