Reasons for this policy:
We have no way of knowing if the thaw protocol sent with the shipment was followed exactly at the receiving institution. If changes were made to the protocol there will be lesser chance of success.
It is recommended that a facility (cryopreservation core, transgenic core) at your institution help you with a successful recovery of the frozen material.
If the protocol was followed exactly and no pups were seen there can be many reasons for failure, which are out of our control. Surgical techniques may not be up to our standards. Environmental conditions may lessen the chances of a successful term pregnancy. Cannibalism may occur.
Our QC (quality control) figures are always sent with the shipment. We include enough aliquots to generate at least one mutant mouse; generally many mice will be obtained from the frozen material.
The only exception to the policy is the material in the shipper was not in a frozen state when it was removed from the shipper, or the shipper arrived damaged or without the locking devices. In that case an adjustment could be made to defray some of the replacement costs.