I am no longer experiencing this issue on ChatGPT for iOS 1.2025.049 (13467804450) running on an iPhone 16 Pro Max (MYWA3LL/A) running 18.3.1 (22D72).
I started a new conversation in the ChatGPT for iOS app and then proceeded to switch to a few different large apps. When I returned to the ChatGPT for iOS app the text was still there. So, I believe that this bug no longer exists in the versions I’ve described above as of 2025/03/05.