If I {Rite of Replication} an {Archaeomancer} can I bring that Rite to my hand from my grave with the Archaeo copy?
In the rulings of archeomancer, I think it talks about exactly that. Says you can put the spell that brings it out back to your hand
oh! thats easy. thank you!!
Here's how it works: Rite starts resolving, putting the 'mancer copy onto the field, triggering its etb. Rite finishes resolving, goes to the graveyard. Then triggers are put on the stack. Rite is in the graveyard at that time, making it a legal target.
Same thing goes for an {Eternal Witness} entering from a {Chord of Calling}, {Wargate} or {Genesis Wave}!
Yes, that works.
It all boils down to timing.
Triggers are put on the stack when you receive priority, which happens after the spell which put the creature on the battlefield finishes resolving.
On the other hand, say you cast a spell with cascade, which cascades into an {eternal witness}. In that case the spell is still on the stack when witness enters (cascade triggers off the casting of the spell, and the spell you cascade into resolves before the original), so you can't get it back.
When in doubt, take a step back and check: what really happens.