I don't need a "theory" to respond to that. The FACTS are clear.
FACT #1: Bob Stevens was the 8th person to show symptoms of anthrax infection as a result of the anthrax mailings. If you believe he was the first, you are woefully mistaken. Joanna Huden at the New York Post was first. A list of the victims in the order they showed symptoms can be viewed by clicking HERE. The fact that Bob Stevens was the first to be diagnosed does NOT mean he was the first to be exposed.
Fact #2: There was a trail of anthrax spores in the postal system from New Jersey to Florida. The CDC showed that trail on a chart which can be viewed by clicking HERE. That trail is consistent with the letter going from New Jersey to Florida, NOT from Florida to New Jersey.
In contrast it's possible to go to the USPS records and tell exactly what vehicle at what time transported a load of "flat trays" from West Palm Beach to the Philadelphia BMC, and then which vehicle at what time transported the same load of "flat trays" from Philadelphia BMC to major mailers in Central New Jersey. I was able to narrow the field down to 4 mailers who might have gotten those contaminated trays (with the letters still in them).
Even the one week difference in cancelations clearly indicates a "beat" you would expect from a mailer pulling trays off a stack.
Check through your materials to find out which "shaker" or "culling belt" was "contaminated" with Anthrax. If you don't find one in New Jersey that's because those pieces came into the post office with OTHER MAIL already in trays, or with other mail in a general "mixed" tray entered by the mailer at the same time he entered his regular bulk and presort rate mail. That tray was taken over to 010, pulled, the few pieces stacked and faced, and then dropped right into cancelation feed.
You really have to get down and dirty to find the specific tracings of the pieces to understand what was happening to them and where they came from. That requires a vast amount of postal knowledge beyond what that chart shows.