I found it--Tarkington's report on Fort in The Bookman:
As suggested by Tarkington's bibliographer, it did appear in the advertising section of The Bookman. The section was unpaginated, but it was attached to the August 1920 issue.
Interestingly, Tarkington is not noted by name. But he did send his query to the gossip section of the magazine, and so it was meant for general delectation.
Interestingly, Tarkington is not noted by name. But he did send his query to the gossip section of the magazine, and so it was meant for general delectation.