You have a bank. The way security works at the bank is that when anyone enters or leaves, they must check in with the guard at the door. They present their ID and, if they work for a company that does business with your bank, the guard lets them in. Anyone allowed in may carry anything in or out of the building freely.

One day, an explosion rocks the building. Many lives are lost, there is a lot of damage, and someone has stolen all the gold in your vault. The security guard’s records were also destroyed in the explosion.

What do you do?