Zebretta
Your situation here could have had a very bad outcome, if you were not there. I've seen threads concerning battery storage, fancy boxes, hotels, etc.
Considering the consequences these little batteries can create, I've been nervous about all of them. Call me paranoid, I guess.
I buy quality cells, but, they can cause the same outcome, eventually. I do not trust any of them.
After hearing of your situation, here, I'm re-evaluating how I deal with my Li-Ion batteries.
They ( I feel ) need to be stored, not touching each other. I think, insulated away from themselves, in their own fireproof container.
A military ammo can large enough to line the interior with 1/2" sheetrock, two layers to the walls, stacked solid top-to-bottom, with holes spaced accordingly for a cell in each.
I'll reiterate, call me paranoid, but I value my home more than any of these potential explosive devices having the potential of taking that away when I (or anyone with any sense to deal with the situation) am not there to deal with it.
Look at these batteries (as mentioned above) as incendiaries. OR, look at these batteries as a stick of dynamite, internally fused.
These flashlights are neat toys. I have just a dozen, now. I can't imagine what people have in their collections, the amount of destruction, that a pile of batteries could cause once one in the pile torched off.
Chain reaction? Dunno.
You, my friend, are very lucky you were there at the time.