If you find something wrong, tell the HR Department to check with the owner of the parcel for the acknowledgement letter or to tell, with the police to run checks.
If you notice any unusual Notify the Human Resources Department to check with the owner of the parcel for a confirmation email. Or to notify the police to conduct further investigation.
In the case of the anomaly. To report to the human resources department in order to check with the parcel for confirm the receipt of a letter To inform the police or even to investigate further.