Suffice to say that the spell is errata'ed:
- special duration at +0 magnitudes
"Being non hermetic, the duration of that spell suffice to cast any spell, ritual, ceremonial or not. It cannot affect spontaneous as normal.
This spell effect cannot be duplicated normally."
That solves things.
AS for the sigil spell, traces of magic may be one of the things vim is able to affect.
Thus it could be used either on a spell in creation, either on the remaining traces. The latter needs a duration as usual, but the former not.
Traces not being a spell, it's ok by rules.