@Li-aungYip 's recent question made me think about this.
From the d20SRD:
This white gold ring continually allows a living wearer to heal 1 point of damage per level every hour rather than every day. (This ability cannot be aided by the Heal skill.) Nonlethal damage heals at a rate of 1 point of damage per level every 5 minutes. If the wearer loses a limb, an organ, or any other body part while wearing this ring, the ring regenerates it as the spell. In either case, only damage taken while wearing the ring is regenerated.
Let's assume my PC wears the ring on his left hand. If his right hand is cut off, the hand would slowly regenerate. But what happens if my PC's left hand is cut off?
Theoretically speaking, the spell was active when his hand was cut, but the channeling (if it can be called like this) got interrupted. If my PC immediately (that said, less than 1 round) wears the ring again in his right hand, would he get his left one back? If the answer is yes (which I don't believe), would he get the hand back even if he doesn't wear the ring again (or if he wears it after 1-2 minutes)?
NB: While I would prefer a rules-as-written answer, feel free to answer anyway if this already happened to you and you used a house-rule!