One guy thinks he sees something, then the next has FOMO, so he says something. The controller has no clue as he can't see out the window. It could be something interesting, but that's about it.
I heard a guy on Seattle Centre call out I'm hearing an ELT on 121.5 , so I stop scanner to listen further, then crickets. Either he went out of my range or I couldn't hear ATC, but silence. So, who knows? This is why I listen to catch these elusive tidbits !