I would agree, but if she could hax her way into Gensokyo, is there really even anything stopping her from traveling to and from the moon at any time? Did Kaguya even really matter much to the Lunarians? Were the emissaries sent to bring Kaguya back simply exiled Lunarians that were sent to their deaths unknowingly? You never know. If anything, Eirin was a much more important Lunarian figure, and they left them alone simply because Eirin was with her. Or something.
EDIT: I should reread IMIE. There's probably an inkling of explanation in there somewhere.
Sorry about this rant here in advance, I just kinda got started typing and it kept going... And it ended up pretty off-topic. Not to mention, you probably already know most of this.
There probably wouldn't be anything stopping Toyohime at any time, after all she was seen using it even after the full moon had passed. Even Yukari can't move between the two unless it's a full moon.
Kaguya mattered to some extent, I'm sure, as she was royalty... But, she's on earth, and it seems that the Lunarians don't actually care that much about earth from what I read (they appear to see watching over and messing with the earth as a game, if anything...). Well, it was said by Eirin in CiLR that, understandably, even if Kaguya had taken the second chance they gave her... Life wouldn't have been the same for her as it was before she drank the elixir. The fact that she had sinned would remain, and Lunarians just can't seem to overlook anything like that no matter what (for example, look at the fact that Chang'e is STILL imprisoned on the moon and the rabbits are pounding mochi there to help take away some of her punishment even now).
The emissaries that went to give Kaguya a second chance back then did find her, and she would have been taken back to the moon by now if Eirin had not turned traitor. Eirin alone is more powerful than Kaguya is (see
here).
Eirin is one of the founders though (and consequently one of Tsukuyomi's most trusted friends), so she would be way more important. And in fact, in CiLR it's made clear that the Lunarians have not forgotten about Kaguya/Eirin/Reisen at all, in any sense of the word. However, the only ones who keep watch over the earth and look for them are the emissaries, which consist of no one but the Watatsukis and some largely useless bunnies. And the Watatsukis say explicitly, also in CiLR, that as far as they're concerned... They'll never find the exiles. Yes, they have found them, but they won't be telling anyone else on the moon that they have because they're still loyal to Eirin.
Since everyone else on the moon just seems to go about their everyday lives without giving a shit about the earth, the fact that Eirin is among the exiles is probably a good enough reason as far as they're concerned for why the emissaries wouldn't have been able to find them even after 1000+ years.
And as far as Reisen goes? The bunnies of the moon have very low social status, so I don't think any of the Lunarians actually care that much if one or two of them go missing (see for example how easy it was for the emissaries to cover up Reisen II's escape just by giving her a different name). The only ones who can use the long-distance bunny telepathy ability are the bunnies themselves, so the one who spoke to Reisen in Kaguya's profile is just a bunny... And in CiLR, it's made quite clear that bunnies just love gossip and you can never be sure whether what they're saying is true or not. Since most of them seem to be such weaklings, they probably did feel quite a bit of alarm at the situation with the humans, but if said humans actually fought with the Lunarians instead of the rabbits? There would be no contest, the Lunarians could wipe them out of existence in an instant (literally, especially if Toyohime's fan has anything to say about it).
Since the emissaries only consist of the sisters (main fighting force, can't just go off and look for a stray bunny during a war) and the bunnies (would never be able to find Reisen), you can see that the threat to Reisen was probably an idle one.
Life on the moon generally seems to be very empty, even if it is much more pleasant. Comparatively, life on earth is much more emotional. Or at least, Kaguya thinks so (this was said in her IN profile). If they care that much at all about the exiles at this point, I would think that's for one of two reasons:
1. Eirin.
2. Potential critical info leaks and rebellion, or something like that.
Since the earth is basically one big pile of trash to the Lunarians, it would make sense that they wouldn't actually give a shit about a traitor who even turned down their offer of mercy. They already see the earth as a place they send exiles to anyway. Eirin's emotion of guilt for what happened to Kaguya has to be more than anything any other Lunarian ever felt for the princess. In fact, their offer of "mercy" to her was almost definitely very half-assed.
So the only reason the Watatsukis would have probably been sent after Reisen (especially in the middle of a supposed war) is if the people of the moon thought they might end up dealing with those issues in the process.
