Newly added column not visible in phpMyAdmin
It looks to me like your bumping into this known issue: http://sourceforge.net/p/phpmyadmin/bugs/4187/
The update goes to cache and therefore teh select * would come from cache versus the select "explicit column" which would pull directly from the DB. I'd imagine the export > drop > re-import process clears the cache with the drop.
Looks like its fixed in 4.1.2