What do you expect to see? When there are answers to small prayers and there are no acknowledgements and no spirit of thankfulness, does one expect to see greater miracles? I think not. Faith is built over time according to the determination of the individual that seeks it. As confirmation upon confirmation situates in the individual, God permits larger and larger miracles. The atheist may be almost completely insulated while great things are happening all around him.
The Bible says many times that requests made in prayer will be granted in both the OT and the NT.
22 And vwhatever you ask in prayer, you will receive, if you have faith.”
24 Therefore I tell you, pwhatever you ask in prayer, obelieve that you qhave received1 it, and it will be yours.
John 15:7 “If you abide in me, and my words abide in you, ask whatever you wish, and it will be done for you.”
Clearly the prayers of amputees go unfulfilled.