How do you tell what image in a thread was loved?

If someone loves a photo, you will see a heart by it, just like where yours is. They layer on top of each other. To see the list of people, you can double-tap on the photo just like you would to bring up Tapback and a bar will appear on the top of the screen with a number of how many likes or whatever Tapback and if there are more than one, you can tap on the person's icon in the box and it will show who actually provided a Tapback.

Then it is very possible we are not understanding each other. I'm sorry, but if you are looking at a message thread and you are seeing that an image received a Tapback of a heart (meaning it was loved), you can see that information as I described above. But, you would need to Tapback on the image. You have to locate the image that was loved. The only way to do that is to find the image that has the heart icon beside it.

The one that has the little heart beside it.

If you saw a colorful circle, then you did something wrong. You needed to follow the instructions in the link I provided. QUICKLY press and release the volume up button, quickly followed by the volume down, then quickly press and hold the power button until you see the Apple logo at which point release the button.

Then can you explain how it is that you think someone else loved an image? Did you receive a message that said someone loved an image? You would only see that in the list of messages, not in the message itself. Otherwise, in the message thread, all you see is the icon.

Then try powering your phone off and back on again. The next step would be a force restart. Force restart iPhone - Apple Support