If for whatever reason, a runescarred character did not have their runescars, or arcane tattoos, could they still use their innate magic?
For example, I was thinking of making a character that had all of his runes on one hand. If he were to be captured, and his hand removed in an attempt to prevent the use of his power (something our GM is not afraid to do in his games), what do you think would happen? Could he still use his powers? Would he still need his runescarred hand? Would it need to be attached to his body, or just in his possession?
In the Runescarred Dedication seem to indicate that "one of the runes on your body corresponds to the chosen cantrip"
So it would seem if someone was to cut off your hand that had say the Shield spell attached to it. It would indeed "cut off" your access to the Shield spell.
The rest is up to the GM so the GM might go with being able to "re-attune" to another scar but that would be during Downtime and not something you could do during an encounter....
This seems beyond the scope of the rules. Your GM would just have to decide.
The solution is to have all the tatoos on the head. If that gets removed you don't need your spells anyway.
Seriously though, what Aratorin says. There are only few rules for amputation and even less rules for their effects.