If I have a Probe returning with minerals back to the base (Issued order "ProbeHarvest",1), how do I know where it was mining from?
I would like to write a trigger which orders the probe to return back to the mineral field early.

To clarify: I have a trigger whose action is one of those:

* order to return resources back to Nexus:

`TriggerAddEventUnitOrder(null, "ProbeHarvest", 1)`
* used an ability to return resources back to Nexus:

`TriggerAddEventUnitAbility(null, "ProbeHarvest", 1, c_abilHarvestStageApproachDropOff, false)`

and in the trigger action I want to learn were it was mining from.

Note: I know how learn when the probe is *approaching* the mineral field `TriggerAddEventUnitOrder(null, "ProbeHarvest", 0)`, but I don't need that information *at that time*.