While Fir Her Waz is a wanderer in this Omniverse, he is not entirely out of the loop. Instead he would need to keep informed of the many happenings in the Omniverse.
That is because his target is the All Source. He knew that once he got his hand on the All Source and the many powers of the Omniverse knew about it, it would be like he is holding the greatest treasure of the Omniverse.
The Seven Great civilization that headed the Intergalactic Alliance, headed by the seven powerful ancient being might not be interested in the All Source.
The fact that they could cover up the facts about the whereabouts of such artifacts is incredible.
If not for the fact that he went to Belthana and met with the Three Fates, he would never have suspected that the artifact is on Earth.
The reason why Fir Her Waz didn't think they would care that much is probably because of how they let it go.