How did an old photo appear in a different conversation on iPhone 15?

i recently was msging someone on my iPhone 15 and somehow a pic someone else sent me a month ago appeared in the convo I was currently in. There was no way I accidentally went to my older convo, found that pic out of many, and somehow shared it with anyone, let alone the convo I was in. I am weirded out how that could happen.

[Re-Titled by Moderator]

Original Title: Pic from a separate and older convo magically entered a different convo with someone else a month later.