He decides to pocket the locket for later use. This might be one of the things he needs to figure out how to get out of here. However, Reeva couldn't see how it was related.
He looked around the room again to see if he could gain any insight from the room. However, he came up with nothing.
Reeva frowns, maybe this room is not supposed to be open from the inside. He tried to push the door again but it didn't move. The only thing he could use was the white mystic that was left inside the grey rob man. If the floor was draining his mystic power, they had to have somewhere to store it.
When he was a smiling man, he was able to see some of the mystic force in the air, and everywhere, the room was filled with Sun church mystic force. So they are hiding his happiness somewhere he couldn't see.