On May first of 1939 the World’s Fair opened at Flushing Long Island. Frank Foster’s work painting a mural for the fair would have necessarily been completed prior to the Fair’s opening. This means that by that time he was out of a job and on the streets looking for work and showing his work again. It is also of great interest that both Bob Kane who had a booth representing DC, and Frank Foster were working at the fair at the same time prior to the opening. The timing is precise that it was just around that time that Batman first appeared in the May issue of Detective Comics #27. The first known copy reportedly date stamped April 19th, 1939. It was a year later in the Spring of 1940 that actual "Batman Comics" first appeared.
Frank did not happen to see the comic book on the stands until moving to Washington, DC in 1940 where with astonishment he first spotted Batman comics on a news stand.
It is beyond any reasonable stretch of credibility that this could have just been a random happenstance. Since there was no one to refute Kane’s claims at the time, it simply became accepted as a fact over time. To deny relevance of the logical stream of events that occurred is simply inertial difficulty accepting facts that conflict with the long held mind set of conventional wisdom. To clear unbiased heads scrutinizing the evidence, there can be only one realistic possibility. It is obvious that the Batman character was stolen from Frank Foster in 1939 while he was showing his work.