I'd sure like to know too. If not something as simple as a return address, then it could have been fingerprints. Other than that, for me it starts moving into tinfoil hat territory. Given the threats we face today, I'd be surprised and even offended if some highly secret methods weren't in place to track down the letter.
I mean, if there were a letter, every printer has some sort of tell when they print something from your printer. It is invisible to the naked eye, but like a gun serial number, a printer also has a "serial number" we just cannot see.
Plus, xir probably crowed about it on 4chan or twitter or even to sane relatives.
I'd sure like to know too. If not something as simple as a return address, then it could have been fingerprints. Other than that, for me it starts moving into tinfoil hat territory. Given the threats we face today, I'd be surprised and even offended if some highly secret methods weren't in place to track down the letter.
I mean, if there were a letter, every printer has some sort of tell when they print something from your printer. It is invisible to the naked eye, but like a gun serial number, a printer also has a "serial number" we just cannot see.
Plus, xir probably crowed about it on 4chan or twitter or even to sane relatives.