Just to clarify: I do not think Codex itself did the rewrite.
My understanding is that the prompt was sent, updated elsewhere, and then the updated version was reported back into the Codex session. That is likely what you are seeing in the search results. 
The reason I mention this is that, for users asking about prompt rewrites in regular ChatGPT, switching to Codex changes where the evidence is stored. In ChatGPT, you may have to find the original and updated prompts in the session history, reasoning/thinking output, or related UI. With Codex, those records may be retained locally in a subdirectory under .codex, making them easier to inspect later.
The question I now have is: did you do this on your iPhone? If so, is the .codex directory actually present on the iPhone, and how long is it retained there?