Common issue, not a bug, something that’s wrong with the human mind, that’s why people can’t find thing that are right infront of them... When I went to find the fragments, it took several days and guides, and I only found it after quitting the search and looked up to see the little shit....

Did you miss the one in the room before Rasputin’s core, on the support of one of the bridges in there, to the right as you go in? That’s the one I missed when I did it. Held me up for ages because it wouldn’t let me back in. Eventually the story mission that takes you in there cane up as an adventure during a flashpoint fortunately so I managed to get it then.