Thank you to everyone who responded. Sean was particularly helpful. Thanks for
the cc, as your message did not turn up here.

Pratia pedunculata (R.Brown) Bentham and Isotoma fluviatilis (R.Brown)
Bentham are two very different species.
Pratia differs from Isotoma in the corolla tube is split nearly to the base.
(Hortus III)
I suspect that the truth is your garden variety star creeper is Pratia
pedunculata, but may be mislabeled as Isotoma fluviatilis.

Now all I have to do is wait until spring and look at the flowers with a
magnifying glass. A related question is which is the one in my lawn that is
hardy to Zone 5?
Iris,
Central NY, Zone 5a, Sunset Zone 40
"A tree never hits an automobile except in self defense." - Woody Allen