Read your contract and see if you were allowed to leave valuable items within it. If they said to remove 'em it's on you.
I really don't think a lawyer is needed in this instance.
Everyone is responsible to take "reasonable care" as far as the law is concerned and this doesn't change from one state to the other although some locales have a looser interpretation than others. This is why many contracts specifically require you remove your personal belongings.
I'd make a report to the local police dept and turn the whole thing over to my insurance company. The ins. co. will probably want the police report anyway.
Sorry for your loss:(.