ya, it's probably toast, but doesn't smell as good.
it could be attributed to a short, but i suspect you might have had (past tense!) a failed "eject" mechanism (corrosion maybe?) in the heating element. for it will continue to heat up until it ejects itself and breaks the circuit's continuity. in order to prevent a reoccurrence of the meltdown, i'm guessing the circuit could be set up with an inline fuse. but i doubt if that's necessary, as it may well be in a circuit that is already fused.
anyway, cigarette lighters have been working in cars for probably a century without in-line fuses. it's just that when they've sat for a while without use and they're old it's sometimes necessary to prematurely pull them out to avoid catastrophe (!).
i've had cause to recently purchase the internals of the cigarette lighter, from Third Gen Automotive, for my '41. but i imagine you'll need to buy the whole darn thing.
they might well have what you need.
