I have no problem with him keeping that revelation from Angelica, it makes sense that a prospect would keep his mouth shut. It's just weird for the author to keep that internal dialogue hidden from the reader given the significance of that knowledge and how often we see his thoughts throughout the rest of the story. It feels inconsistent for a VN whose storytelling style is very blunt and straightforward to take this brief departure into vagueness/subtlety before going right back into the original straightforward style in the next chapter. It doesn't need to be explicitly spelled out in Ryker's thoughts, but a simple internal 'What the hell?' that never gets expounded upon when they first find the ring or a brief side-eyed look at Stan as they're leaving after bringing the ring back would go a long way while still leaving room for doubt if that's what the author wants.