Hi
I think it's credible to have a photographer want to know what happened to the subject of her prize winning photo but I'm not sure why she would need to discover this to retain her credibility - photographers in these environments often don't know their subjects - I'm not sure if there would be an expectation to either.
If however it was the case that the subject of her photo needed help and the photographer didn't provide it - choosing art of humanity - I could see why people might question their integrity. I believe there was a prize winning photographer who commited suicide after being criticised for taking a photo of a young boy being attacked in the wild rather than intervening and helping.
Maybe up the stakes. Who is threatening your photographer/making them obsess over the subject of the photo and why? You may already have this as the story - if so, reflect it in your logline.
good luck.