The pain came later, after the operation to tidy up the stump (long before they started stitching them back on again). Why?

Strollin Johnny, what you're describing is called "phantom limb syndrome". While the physical body part has been lost, the nerves and brain area that controlled it are still intact. It takes quite a while for the body to adjust, to "realize" that the part is gone. Until it does, pain and other uncomfortable sensations (like the limb being twisted out of position, or twice as big as usual etc) are VERY common.

This makes for quite the tortured existence for a while. People who've had a foot amputated often complain about the lost foot itching constantly, and not being able to scratch it ... and lying awake all night just DYING to scratch it ....

daylia