Doesn’t exist. Some metals can form organometallic complexes (with CO, CN, methyl groups), in which case you get for instance “organic mercury” compounds. Iron can also do that, but that’s not what theyre talking about here.
What they mean is “biogenic” iron. The snail precipitates dissolved iron and sulfur in the water to form its shell out of iron sulfide. Its a different physical structure, but chemically similar to iron pyrite (fools gold).
Hypersonic heating is really weird. We only have data going to about mach 17 (the HTV-2 was the fastest solidly atmospheric vehicle I found) but as we go from subsonic, to supersonic, to hypersonic regimes air becomes pretty much incompressible, and forms a really solid shockwave in front of a fast-moving object. Air is a pretty good thermal insulator, so for very fast, blunt objects they actually heat much slower than you might expect.
Tl;Dr it absolutely vaporized, but it likely lasted longer than you might expect.