It's a boy thing, maybe just an age thing. I say cut him some slack since he didn't lie or pitch fits and yet or protest ridiculously at your drug testing. (He didn't, did he?)
My son is 13 and he too, LOVES anything to do with fire. I try to find healthy ways to let him be around it without creating a temptation and yet not making it taboo either. Fine line, I know.
He is acolyte at church (the one who carries the flame up the aisle to the altar and lights the candles, and also extinguishes them and carries the sole remaining flame out at the end of the service). So he gets to light the "candle lighter" from a match or bic lighter or whatever as a "duty". :)
We also burn yard debris sometimes, and I'll let him light the stuff. He thinks it is great to maybe pretend he has some sort of man vs. wild thing going on. They LOVE roasting anything over the fire (hotdogs, or smores, doesn't matter. Heck, they'll just hold sticks to get them lighted, then wave them around until the end only glows of embers).
My husband grills on a charcoal grill regularly, more in the summer. It is now our son's duty to clean the grill grate beforehand, and then he gets to light the charcoal (under husband's supervision).
He loves "tricks" like putting a paper cup full of water onto a pile of embers/fire, to see how long it takes before it explodes/spills the water. (hint: it can take a while).
Perhaps you could look for some normal/natural situations where it might be "ok" for your son to be involved with fire. It's like science and coming of age--think of how powerful prehistoric man must have felt when they mastered "fire". Your son is on the cusp of manhood. It's VERY age appropriate that he is fascinated by it.
And having him write a paper about the dangers of playing around with fire, or whatever along those lines, is not a bad idea--if you want a discipline action for having HIDDEN the lighter. Perhaps you might consider designating a place in your home/kitchen where all fire paraphernalia must be kept when not in use... ?