Very warm air bag/horn cover

I have a 2015 Access cab 4x4 with the SR and convenience package. It has just under 20K miles on it. Today I noticed that the center cover of the steering wheel was very warm after the engine ran for a few minutes. Nothing else was near as warm. The horn works and the Airbag light comes on and goes off as it should.
Has anyone else noticed this? I guess it could be warming by the sun, but just seemed odd that nothing else was anywhere near as warm.
I have a hard time believing it is a short... Wouldn't the start diagnostic catch that and keep the light on?

 

there is nothing under there to cause heat up

it is a plastic cover on top of an airbag and nothing else
is there except material designed to blow up in your face w/o killing you

no metal, wires, or anything else. the horn is activated by the entire assembly being pressed in

must be sun....

unless the airbag assembly is heating up from underneath, and all the
heat is migrating through the folded up airbag and to the surface

seriously there is nothing but switches in the wheel, and tiny led for the
stereo controls, but that is all to the sides, nothing in the middle but airbag

 

I believe you are right about the sun. Crazy though that the center heats much more than the rest of the wheel.