I am very sorry for your inconvenience. You need to call Apple back and ask them to initiate a claim for the missing i-Pad. They will then ask UPS to initiate a Driver Follow Up, which is our way of asking the consignee to verify whether or not they received the package. In your case, the DFU will be for Signature Denial. The DFU will also have a Google Earth image of the location of the DIAD, which is the "computer" the driver carries, at the time of delivery. As Scratch mentioned, the driver would need to be within 200 yards of your house for the delivery to be considered as having been made at the right address. As for the signature, the signature that was used to record the delivery will be on the DFU. You can also see the signature if you track the package at ups.com.
A driver forging a signature on a package could be grounds for termination so please make sure that you have your ducks in a row before going any further.