Of the three known Hammett short stories that have never been reprinted, one has not yet been found, and the other two never have seen reprint in either a Hammett collection or some random anthology.
Scanmaster Evan Lewis has tracked down “On the Way” from a 1932 Harper’s Bazaar and tossed it on his blog so you can read it, if inclined. He tells me that “it’s an interesting take on his relationship with Lillian Hellman — sort of a counterpoint to The Thin Man.”