Is it a perennial or annual?

my big book [RHS Plant Book] has several Cuphea but some are short lived and others annual. Does it have a second name after the cuphea? there is a C. pupurea that is a sub shrub and short lived. I'd do the normal scratch test. thumbnail on the stem if its green under neath it is still alive. I'd trim it back and water sparingly and then wait and see.
some one else may have this and know better. hope this helps.