You're right that the signature on the rendering (Chuck Kirby) is an artist not the architect. However, I found the link below which provides an address for Mr. Kirby. Perhaps if you contact him, he would be willing to look through his records and tell you who the architect is.

Here is a link that might be useful: Kirby Illustrations

This link will take you to the designers they use:
http://www.eplans.com/house-plans/epl/designers/designer-9922/hwepl14393.html

You could also call cusromer support and ask them if they
will disclose name of architect for this plan- 1-800-528-8070

Here is a link that might be useful: http://www.eplans.com/house-plans/epl/designers/designer-9922/hwepl14393.html