I just found out few days ago --
I bought a new sneaker. I was wearing a sweater with polyester jacket on top. Routinely I get static spark when I touched any metal part of car. I hate it.
Now, I went to gas station then got out of car, I avoided any contact with metal part of car. I opened the gas door, removed the cap, inserted the gas nozzle into the gas tank, I touched the metal part of gas notch, I FELT the BIG spark! Luckily for me it didn't ignite the gas.
Point in this story is rarity, it doesn't happen to many of us, it is probable that what happened to me HAPPENED to them, not the cell phones? People saw them on phone, talking before the explosion, blamed all on phone but in reality it is actually the way they are wearing, charging themselves up with so much static electricity, then when they discharged somewhere near gas nozzle that gas exploded?