Detective Work
Although the FBI didn’t believe that there was any truth to this letter, the possibility of finding the only survivor of this infamous escape from Alcatraz definitely intrigued them, making it impossible to ignore.
Although the idea of reaching out to the FBI in an attempt to cure cancer seemed somewhat feasible, they also figured that taking this course of action at his old age was a bit unrealistic, so instead of jumping to conclusions, they decided to go a different route.