Same here, the left speaker cover was sticking up and I just pushed on it till I heard a click and all seems to be good again but I will be keeping an eye on it.
It might also not be heat related, as to why the speaker grills are popping up like that. It could be the unibody design, I do live on dirt road, and we occasionally get washboard or ripples. Although, since I got my grill down I haven't had it come back up either. Time will tell though! Lol