Was it? Is it missing?
If someone grabbed the numbers of your credit card and used it to buy stuff, would you report it stolen? Or you would think that since you still have your card nothing got stolen? Same thing here.
And when did we mention anything about person B? Where is this person? How does this affect them in any way?
Pay attention, person B is the artist who's not getting hired/commissioned and/or whose data was used to generate the image. Which is why I said I have no issue with personal use, the artist wouldn't have gotten hired to draw an artifact that I will show for 5 seconds to my RPG players, no harm no foul. However if I was running the game on YouTube, or otherwise earning money from it then I should pay for it or not use it.
When I learned to play guitar did I steal the chords? I certainly learned to play other peoples songs, did I steal those too? I am now influenced by those songs, did I suddenly take away someones livelyhood?
If you recorded and sold those songs you would have quickly found out that there are copyrighted. This is the same case, we're talking about someone profiting from it, not using for personal use.
In any case, so if I understand your argument: if the data was trained on publicly available data, you wouldn't care.
If it was trained using data that the creators gave explicit permission for it to be used in that way then no, I wouldn't have any issue with it. But publicly available data to view does not equate publicly available data to train a model, same as it wouldn't allow you to print it and sell copies. Displaying something publicly doesn't give you ownership of it.

