DCI Level 2 Judge
Do you mean you targeted an aura spell to spellskite, or that you targeted the triggered ability of an enchantment to spellskite?Also, was the vapor snag cast in response to spellskite's ability or after spellskite's ability had resolved, redirecting the aura/ability?
That depends on when they actually vapor snaged it. The spellskite's ability uses the stack like most other activated abilities, so if your opponent vapor snags it before the spellskites ability resolves then when the spellskites ability resolves and tries to change the target of the aura it will no longer be a legal target so the target would remain the same and the aura would resolve normally. If however they wait until after the spellskites ability resolves then vapor snag it, at that point the aura would be targeting the spellskite already, so when the aura tries to resolve it would be countered on resolution for having no legal target.
Do note that if the opponent casts vapor snag in response to the spellskite ability, you can just activate spellskites ability again (provided you can pay its cost) and in that case the spellskite's second activation would resolve before the vapor snag and change the target of the aura (sending it to the graveyard when it tries to resolve).
This I'm a bit confused by. So if target the enchantment, the y target spellskite with the the vapor snag, I can in turn target the spellskite with the spellskite even if it's already targeted?