An insect’s shell contains silicates that make it harder than the blood proteins that were in the bone.
Your assumption of absence of moisture or air are absurd. If you’re going to try to say that any part of the bone was fossilized, moisture and it’s accompaning air have to b e present. Ask your evo pals, and I’m sure that they will straighten you out on that.
Proteins are known to survive up to ten million years. This latest find was unexpected, but the conditions of fossilization are unusual.
I'm going to ask again for your documentation that this is impossible, rather than unusual.