iPhone 17 Pro missing Photos tab in Messages after iOS 26.1

Sorry, it was very late when I replied. Yes, you are correct and you are on the message page. When did you updated to iOS 26.1? If can take hours to a few days for all the data, including photos to index. Once the full index is complete, the Photo Tab should reappear. If it's been a few days, Force Restart your iPhone and see if that helps --> Force restart iPhone - Apple Support

You've opened a persons contact. That is not where Photos appear. Open a text message from someone who you know has sent you photos. Tap their name at the top of the message, then look for and tap Photos. All of the photos they've shared with you, will be shown.