Iphone 6 bent from heat of direct sunlight?

Gday, my iphone 6 is only a few weeks old and has never been placed in back pocket, no skinny pants, never mistreated or dropped always been in a decent bumper case (spigen ultra hybrid) and after a day at the beach in about 28-30 celcius heat I noticed my phone was slightly bent in the usual places near the buttons on both sides with the screen being the inside of the bend and the screen managed to stay reasonably straight so you could see the slightest gap between the screen and the very inside of the bend. The bend was slight but still noticeable If you were not looking for it. My phone was placed screen down on a towel in direct sun only for about 20 - 30 minutes and it did start to feel quite hot. Since I really cannot remember it accidentally being subjected to any force that could have caused this. my guess is the heat.

I very carefully bent it back with my hands it is now pretty much perfect again. So im only guessing so this may or may not be thing but for obvious reasons maybe try not to leave the iphone 6 in direct sunlight or exposed to heat for too long to maybe decrease chance of warping. Aluminium good at absorbing heat And all. (Just wish they made it stronger)

thanks.