I agree, Chronos - reasoning has to be crystal clear - no breathing space for apologetics allowed;)
I just find that many people have no idea what to expect for someone to physically grow back a limb. It is indeed inconceivable & un-imagineable. But is it? No, in nature it is possible for some vertebra to grow back limbs. Nothing more said. A mention of this fact makes it very real and it could highlight the uncomfortable situation that the god-of-healing is plan-less when it comes to his very own children.
With regards to the second point/reasoning that was made - I would like to see how you feel about it or will christians just ramble on that god will not be tested etc: "The reasoning is basic: If god do listen to prayers of the believer - then believers should have a onger lifespan than non-believers - on average. Is this the case? No."
Apology for the English (not my first language