Your refering to the amp fuse and not the inline fuse that, should be, is on the wire from the battery to the amp?

Is it at all possible that something metal could have come in contact with the amp during that time? Like a loose screw or pliars or screwdriver rolling around the trunk? It's possible something could have rolled against the amp and shorted it, in which case I would just relace it and find the offending bit of metal.