[Diamond]

Those sensors would have picked up and relayed the signature of atomic detonations, which would have brought on an investigative mission.

And how much time would it take for this information to reach its destination?

Cordially,

[Windflier]

And how much time would it take for this information to reach its destination?

Come on and stretch a bit with me, friend.

If a civilization has the ability to move across interstellar space at faster than light speeds, don't you think they'd also have the means to communicate over those distances with the same (or similar) methods?