I went out and took another look this morning. I'm leaning towards maybe R. hispidus but...
Here's a couple of pictures showing it does have some hairs, even though I couldn't actually see them with the naked eye, they come through in close-up photos.
There are a few 'whiskers' on the stem and more on the flower bud ~
Overall view of the plant this morning, the flower was still closed
I'll see if I can get a better look when the sun moves farther away.
