It is always unfortunate when lost combinations or keys take place.
There are really only 2 options in the situation.
1. You can go through Honeywell (they own/have the Sisco line now) and obtain the combination/keys.
CLICK HERE for their required procedures
2. A locksmith could crack the safe, but I am sure the expense will be something to determine that avenue or not. Plus, I am sure they too will have safety protocols in place to insure someone owns the safe before opening.
Those are the only options, as the safe industry has their protection procedures in place to protect the owners and verifying because of the possibility of theft.