You're not credited for the photo. Is that usual?
It's not uncommon when the cover is used as a thumbnail to market the magazine. For example, see this page - http://www.condenet.com/mags/vanityfair/.
Jeff Spirer
Photos: http://www.spirer.com
One People: http://www.onepeople.com/
Surfaces and Marks: http://www.withoutgrass.com