After the firefight at Buckley Bay with the Sons of Liberty, Colonel Thomas Bushell and Captain Samuel Stanley collected what evidence they could from the Sons' midden. In addition Lieutenant Morton Green had his men search the bodies of the dead Sons and the prisoner and handed their effects over to Bushell. One of these was a letter signed "Joe".

On the return trip on HMS Grampus, Lieutenant Commander Edward Woodbridge gave the two the private use of a small compartment to go over the evidence they had. They first went through envelopes since they had postmarks and dates on them. As expected, they were from all over the North American Union, including New Liverpool, Boston and the Pennsylvania coal mining country.

One in particular was franked not with the usual NAU stamp but with one with a lightning bolt and the legend "Heno the Thunderer" and "The Six Nations". It was postmarked "Doshoweh" and the date "18 June", less than a week earlier. They then searched for a letter with a matching date and found one that had been on the person of a Son. It had no address and was signed only "Joe" but said "Stop sending rifles at once. No point to drawing unwanted to ourselves".