Bah! He doesn't answer the damn question. He says why amputations happen, but he doesn't say why won't God heal them.
What he claims to be a miracle of God is actually people with an immune system strong against the infection. Yes, I'm sure people appreciate that having an amputation has saved their life, but that does not change the issue, but rather it dodges it. His answer only opens room for more questions, why will God heal them but not the others? Why did God let some die and others live? Why did God not heal them before they needed an amputation? Why didn't God fix the amputation after it happened? Why do they have to live a life missing a limb whilst the others got away better. Sure it's better than being dead, but not better than having all of your limbs and being alive.
However, the question is about prayer, but people rarely seem to read the site beyond the question and then pretend they've read the site. The part about amputees? Well diseases can be cured naturally and using medical science, amputations are never truly 'fixed', the limbs can be replaced, maybe with a transplant or prosthetics, but you don't grow that limb back. God's miracles are only mundane and ambiguous, never anything definite and when they're supposedly definite, conveninently we can never get the data to measure it. This method is more measureable, we can see if we're talking about a genetic mutation or a miracle from God. God promises to answer prayers, so it's an incredibly important question to ask. Yet, it's one folk don't ever seem to get.