If Fat Boo was close to SSjin3 Goku...

[Let's Go Fearless!]

And how did Bu find Goku FPSSJ if it wasn't through their Ki? We know the power of a FPSSJ could be sensed from that distance, and Bu clearly was above that.

The way they were sensed was different.

And what's that difference exactly?

Pure Boo tried to sensed them while Gohan didn't tried to sensed Goku, but Goku's power was strong enough for them to noticed without actually sensing it.

 

[p123]

Kid Buu didn't sense them, he looked for them. Goku couldn't sense Gohan until he was in Otherworld. No one can be sensed from that far, there's no evidence for it!

 

[Evil Vegeta]

Boo's vision must be on some Supes shit if he can see that far.

The way he looked and smirked gives the indication that he either sensed them or saw them. Can go either way. Super Boo sensed Gohan from far away, but we know he didn't know he was. Probably just some sensing going on.

 

[p123]

Yea, I think it has something to do with Kibito why Kid Buu can do that, or perhaps it's his own thing. Gohan being sensed by Super Buu makes sense, he's way stronger than Goku duh.

 

[Papasmurf]

Remember when he blew up a bunch of planets on his way to Goku and Vegeta in the anime and none of those guys were wished back?

 

[p123]

Kid Buu merely is looking around. And poof finds them. Goku could not do the same on Earth. Goku has to concentrate to find ki. It's not the same. He's doing something else. He has God tier eyes apparently.

 

[Male]

Ssj3 Goku was def the stronger of the two, there is no doubt about that. Lol

 

[p123]

Stronger of what two?

 

[Evil Vegeta]

Yea, I think it has something to do with Kibito why Kid Buu can do that, or perhaps it's his own thing. Gohan being sensed by Super Buu makes sense, he's way stronger than Goku duh.

What doesn't make sense is no one else catching it. Piccolo and the others never even sensed Gohan until he got near them. Then again, this is the same saga where Piccolo couldn't sense Dende until Gohan told him to do it, so

Piccolo also sensed Kid Boo's Chi disappear even though Gohan should've been able to do the same. The fact that he had to tell everyone this implies they didn't sense it--especially Gohan. I think the Chi-sensing from a distance stuff is random and overall hard to use to pinpoint any consistency.