Sorry to hear about this Dan. I can tell you I worked with the postal police on one case where I used to work in a Twp. They came in and told us what they were doing and where the mail lady would be at. They had a tracking device in one of her letters. Bait, hook, line and sinker. Stopped her right in front of our PD. She had a warrant as well. Needless to say she is no longer a USPS employee. She actually fled the country to avoid prosecution! She came back and cuffs were on her at the airport.
The postal police rule btw. They have all kinds of cool items.