I have a trap ability which is based off a sentry ward, and when it deploys I need to destroy the ward, however GetSummonedUnit() doesn't reference the ward...any idea on a native function which would allow me to target that created ward?
I think Last Created Unit only works for units created from triggers. You could try detecting the ward through unit grouping and getting rid of it that way. I'm assuming that you're using JASS, so this probably isn't of much help.
If you say ward placing doesnt trigger summon events then an alternative would be to make a custom ability (channel) and trigger the creation of the ward at the point which the unit casted the spell (or random point around caster if its an immediate ward summon). Now you have a unit reference to apply timed life or do whatever it is you need to do.