that's actually his tutelary divinity who intervene
Not exactly, it could be his herald, or some being that serves him. Direct divine intervention is pretty damn rare and should be saved for rare moments in history, like the closing of the Worldwound or a new god ascending through the Starstone Cathedral.
Golarion's gods are known for (almost) never interfering with the material plane, unless something of catastrophic proportions is going on (see Rovagug). But that's something of the setting and not valid as a rule.
Now, who answers this plead? Well, any being who should be listening and has something to gain from it. Normally it's your god and his servants, as you are a faithful follower of their ideals. But this could also mean any outsider with enough power to carry your request, as long as your ideals and beliefs match.
So a cleric of a concept of Good and Nature could be answered by some Chaotic Good outsider, or demigod, or god. An oracle would call for powers that are likely related to whoever granted her the oracle powers she has. And a mythic character, probably whoever granted him his mythic power, or is the source of that power, or even the character's willpower allowing him to shape reality based on his faith on what he believes (why not, the GM has that power here).
Pretty much any Archfiend (devils) could answer the requests of a Lawful Evil cleric with no deity, for instance. Most would be rejoice if they could talk to someone that powerful and maybe seduce her to be a follower.
For a mythic character who can actually grant miracles to his followers, the GM could send him dozens of small notes with small requests each day (prayers). But when a powerful follower capable of casting miracle, he has the chance to personally answer the call, teleporting to his follower and use his own abilities to solve his problem.
Long story short, you pray to your deity, or powers that you believe, but who they send, or if they appear personally to answer the call, is up to your GM and how awesome he wants that scene to be.