Therefore the immune response you develop wouldn't be to a "known" anthrax or sub type but to another bacteria altogether. Since the anthrax antibodies are different than those you screen for, your test will be negative.
If the correct culture media wasn't used to screen the patients or if the serology tests weren't placed in the correct tubes for storage, transfer, or analysis then the tests would be "negative" but the patient will still have the disease.
The key is if the patient gets "better" or doesn't die if the appropriate antibiotics( doxycyline, penicillin, ciprofloxin) are started.
Even if you live, inhaled anthrax is a mother and may result in permanent lung and heart damage due to the lung problems and even if treated has anywhere from 45-75% mortality rate.
Interesting possibilities.
I wonder how much antibiotics they were giving him.
It's possible, that after their tests were negative they stopped the antibiotics -- I wouldn't put it past the doctors.
Your thinking is right on! Good work.
BA, did you read this?