This could have been the end of the Spirit, but Will Eisner was a smart businessman as well, and owned the rights to his character....and ended up having 2 comics of the Spirit in the 1960s at Harvey Comics (known more for characters like Richie Rich, Little Lotta, Little Dot and Casper the Friendly Ghost).
Harvey Comics Spirit #1
...with 7 other stories from 1948 and 1949 newspapers, and an "interview with the Spirit" by Marilyn Mercer, as well as a 2 page featurette by Will Eisner called the "Spirit Lab Invincible Devices".
Not bad for 25 cents (a large amount to spent on a comic in those days....it was a "Giant Size Harvey Thriller" after all!).
Harvey Comics Spirit #2
There was a two page text feature by Marilyn Mercer wherein the Spirit answers your mail...as well as a 2 page story likely inspired by the Man from U.N.C.L.E. by Will Eisner in the "Spirit Lab, The Man from MSD" as well as 7 different reprints of newspaper features from 1948 through 1950.
These two comics showed the Spirit (and Will Eisner) was able to adapt to the times, and find a home no matter the odds, dealing with everything including the kitchen sink (ironic, as Kitchen Sink Press was the next home of the Spirit in the 1970s!).