Conclusion
He heard the voice of the Patron God as he tried to read underneath the lines of the words that his Patron God stated to him, noticing a hidden warning stated by his Patron God.
Samiel already got hints from his Master Menuhyutt Faulhaber that turbulent times were coming to the Cosmos and now even his Patron God was saying exactly the same thing.
Instantly, after he heard the words from his Patron God, everything disappeared and reality returned back to normal like it was before as he was standing in the middle of the ruins of the Temple of the Church of Lolth.
Yvraine was looking at him while waving his hand in front of his hands because he appeared to be in some kind of trance.
This often happened when the reality was warped for someone, especially for Samiel, who had experienced something like this already several times, because every time when his Patron God summoned him, he would also do it through the reality-warping...