Use registered mail, it costs more but is way more secure,requires a signature at each hand off and it is kept separated from the rest of the mail.
This. ^^^^^ Using Priority mail, anything insured for more than $500 gets same treatment as above. Have had multiple USPS packages go AWOL. One more than 3 months. However, other than a one or two day delay, no issues with anything insured for $600 or more. And tracking has always worked...
