Steve,
I've seen references to Logan, but there is no indication it still exists in that particular location in Indiana. Today, Stemm is an unincorporated community. Stemm is said to have been established as a switching station on the Monon Railroad. Not sure exactly what that means. There may have been some spurs around Stemm that led into some limestone operations.
The Wikipedia reference to Logan (in Lawrence County) is identical to Stemm in that it is also described as established as a switching station on the Monon Railroad.
They've got to be the same community that changed name for some reason.
George L.