The first thing that went through Alex's mind was that he couldn't believe the Alchemy God was not only openly displaying where his knowledge of Alchemy came from but also was asking others to show the books if they had it.
Given that, there were 3 books in total and he only had one, the chances that one of these Alchemists had another one of the books was sufficient enough for him to see that here.
Then the next thing went through his mind, which was anticipation for another one of the Alchemy God's books to come out during this assembly.
His head turned all around the place, a part of him expecting to see someone pull the books out. He did not even consider that people could be intending to hide it if they had it. He was a little overwhelmed at the moment from the surprise.