This name is a synonym of Phlox kelseyi var. missoulensis (Wherry) Cronquist.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 100363336) with original publication details: Notul. Nat. Acad. Nat. Sci. Philadelphia 146: 7, f. 4 1944.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:193585-2.
This name was in version 1 of The Plant List, record tro-100363336.