Why doesn’t lava melt people?
In addition to the “bones don’t melt” answers which can be supplemented with “meat does not melt”, it is interesting to note what happens on the rare occasions that people have fallen into lava.
The lava is very close to its freezing point as it oozes across the ground- it is basically just barely molten. When something falls into it- we’ll say a leg in this case- the lava freezes around the surface of it to create a rock cast. While this burns the crap out of the object, it can also help to insulate a person from being further burned since the hard rock cast will now prevent liquid lava from continuing to contact the hapless victim.
You can see what happens by observing lava casts of trees. Generally, the trees themselves burn away as the lava flows around them, but once the lava flows away (if it does), you can have a forest of casts left behind. When I worked at HVO, I was told of a scientist many decades ago who fell waist-deep into lava and survived it, though badly burned, because of just this effect. Try as I may, I can’t find a record of this incident on Google (probably because it predates the internet by several decades).
Here are a few photos of tree molds at Kilauea from my time working there. Excuse the terrible quality of my photos, digital photography was not far advanced in 2003.