I store all my rods in a rack I made years ago. They're stored vertically in a spare room.                             Im not sure that " warp" is the best term here. Years ago, fiberglass rods could become warped if leaned in a corner in a hot room( attic, garage, etc).                     Can graphite rods do this also?

The only thing I’ve seen with graphite is high heat causing failure. Even a hot car shouldn’t affect a graphite blank. 

The first gloomis rod I ever bought I left in my car on a very hot day, it was over my seat pressed against the roof with a slight bend in it, and that is the shape it stayed in from that day forward. Good thing I got it off a friend used for $75 or I'd have been very po'd. So in my experience, yes they can warp.