I have no experience with Cecile Brunner, the short polyantha, which most sources describe as thornless, but I do have the climbing Cecile Brunner, which is a sport of the short one, and it definitely has thorns.
I wonder how common it is for a thornless rose to produce a thorned sport. This raises doubts about the accuracy of the information that the short polyantha is thornless.
There's another possibility. There's a rose known as Improved Cecile Brunner, described in various sources as a floribunda or a hybrid gigantea. It has thorns and it grows to only about 3 feet tall.
Rose (Rosa 'Improved Cecile Brunner')
