Keltham sees it through the screen, out of his peripheral vision. The note is in large letters, but it's hard to read up here, through the screen.
Not particularly thinking about what he's doing, Keltham casts Prestidigitation, then turns the screen near-invisible. A fly, apparently startled by the event, buzzes away. Keltham isn't focused on that part consciously; he's still having a bit of trouble reading the note, so he grabs a lens-shaped volume of air and changes its refractive index until the note enlarges in his vision and becomes visible.
Something in the back of his mind notes that Keltham maybe really is become a magic-user, now, something that belongs in Golarion and couldn't use all of itself elsewhere.
...his books from Tien have arrived.
Good, Keltham guesses.
There's a developing sick feeling in him like maybe he doesn't need those foreign-language books. Is there a point? A Conspiracy that could fake the Chelish history section of a library has had time to pick nonproblematic books out of a distant place that doesn't think much about Cheliax, and maybe try to quickly censor or edit those...
And yeah, if Keltham is feeling that sick way about things - like things are going to fall apart as soon as he takes the items on his list, and starts looking for connections and ways to fit them together - then maybe it's time for him to, go ahead, and finish this, if his mind already knows where it needs to go.
Carissa is sitting on the grass, below him, looking cheerful, as Chelish people do, messing with her headband-manufacturing-assistive devices.
'His' Carissa.
Keltham's not - not really reasoning it through carefully, when he does what he does next. Before that. It might be a giveaway. The Conspiracy is reading his mind anyways. That's not certain, the Rope Trick could defend against it. The Conspiracy wouldn't have told him about Rope Trick if that was a real possibility -
Keltham just does it anyways.
He writes a note, and carefully pushes it out of the Rope Trick, underneath the edge of his Prestidigitated fragile screen.
So, what does Conspiracy Carissa think of Keltham?
Obviously Conspiracy Carissa's simulation of Ordinary Carissa, won't really know. Or will say something Conspiracy Carissa thinks is useful, though, if it's visibly useful, to him, it leaks bits. Maybe, if they're reading his mind, and if they're expecting him to figure it out, they're past worried about leaking bits, and will say something else carefully designed to manipulate them -
Keltham doesn't know why he's doing that.
For whatever it's worth, if they're reading his mind, he intends - to compute things without whatever Carissa says, he won't consider it in his evidence for Conspiracy, or against it, just like if he found somebody with a missing head and needed to figure out without that whether they'd been murdered. Keltham can't really do that, he's not smart enough or wise enough to be a judge in a court of Civilization, but he can just, read whatever it is, and then put it aside and not think about it while he's adding up the rest of the evidence.
She said that to him, that she knows exactly what Conspiracy Carissa thinks of him. Maybe there was a reason Carissa said that. So he'll ask.