They took our stuff ???

I live in the state of Kansas, recently my father went to our storage shed to remove some family items, when he got there the room was empty. Apparently someone with a power of attorney form was looking for a "storage space" with the same last name....the first names were different the addresses were different in fact the people who removed our belongings went to the wrong storage company and just lucked out that there was someone listed with the same last name. The person working that shift went and cut the lock from out storage and the people removed everything. The people who took the stuff didn't know the person who's property they were getting so probably didn't even realize they had done it. They took our belongings throwing some away selling the rest. Some of the items were original auto parts for an antique car that can't be replaced. So my question is I know the storage company is liable but how do you put a fee on items that are not replacable? The owner of the storage company said he would reimburse us for our loss so how do you determine an amount....sue for stupidity?

Thanks
Thanks