This name is a synonym of Phlox drummondii subsp. tharpii (Whitehouse) Wherry.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50229548) with original publication details: Amer. Midl. Naturalist 67: 280 1962.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:193478-2.
This name was in version 1 of The Plant List, record tro-50229548, and has not been changed.