Cuttings from greggii are not easy this late in the year, bottom heat will help, but certainly dig up any that you don't want to lose. Young plants are not as hardy as established ones. Your seedling sounds great....do you have a photo?

I am short a camera. I was going to do exactly as you suggested and go bottom heat. This particular plant must have survived last winter as a seedling. It is in a 700 foot row of greggii and microphylla where I let the seedlings grow as the seed falls. Now and then something interesting appears. This may be one that suffers from petal whitening, so my excitement may be moot. With so many interesting cultivars already on the market it is hard to find anything really exceptional flower wise. I have no interest in marketing anything, I am just hoping for better cultivars for the local conditions.