Without getting mired in what-ifs and other speculations...
Hardly nowhere. Shira Brie was a Rebel pilot who turned out to be an Imperial spy. She tried to take an opportunity to shoot Luke down when it would be easily attributed to the TIEs they were fighting. Luke felt the hostile intent toward him as a twinge in the Force, dodged, immediately returned fire -- and was horrified to see he'd "missed" and shot down one of his comrades. He didn't know until later that she'd survived and been rebuilt by Vader into the Dark Lady Lumiya.
More that George had other things to do than keep up with it. He roughly knew Splinter of the Mind's Eye, as ADF was working from notes George gave him. And there was such hoopla around Heir to the Empire's release that he couldn't ignore it. He liked the name Tim had come up with for the pre-Imperial name for the Republic capitol, and later included it in the Prequels. But apart from that? He reserved the right to overwrite any or all of the EU not because he didn't like it, but because he couldn't be arsed to know what was
in it.
And from this does dramatic narrative arise. Bonus points if you have good dialogue to this effect in said narrative. "But the Dark Side was supposed to have been destroyed! Wasn't the balance restored?" "Sure -- what made you think that meant forever?"
I figured he just took it everywhere with him. If it's the only way to navigate into Sith space (nice EU callback, that), and he never knows when he might need or want to hit up the seat of his power, it makes sense to me he wouldn't leave it behind in his private quarters on Coruscant. Heck, maybe the third guy from the left's job is to pack and unpack it every time Palpatine goes somewhere:
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