There is no guideline that says a basement has to be "cooled" for it to be included, some agents need to read up. It also does not have to have CENTRAL heat. It has to have a permanent heat source only.
The appraisal forms and the way they are written has changed significantly since 1999, they are even harder to read now,
A single family residence is measured in terms of above grade living area with the basement added yet not in the GLA.
The quality of the finish is the ultimate test of how much value it has in the market.
If the basement is truly finished out I don't think the appraiser would exclude it from his value calculation he/she just placed it on the proper place in the appraisal. Finished Basements are reflected as below grade square footage and the appraiser has a responsibility to look for comps that would have similar below grade improvements. There will be adjustments on the appraisal either increasing or decreasing the value of your house based on the amount of finished square footage compared with those of sold properties.
Was the basement permitted and approved? Although your appraisal didn't list the basement square footage, you can still list the square footage in the future when you choose to list the home. For the MLS you can use the tax record square footage (which should include it if it was permitted) or a professional measurement rather than the prior appraisal.