In the same way that the chester eyebone, hutch fishbowl, and the glommer flower leave your inventoy when you leave the server, the clockwork sketches should leave your inventory as well. If someone in the server leaves with the clockwork sketches and never comes back, then it seems impossible to get the atrium heart necessary to fight the Ancient Fuelweaver, which means you can't regenerate the ruins or the Ancient Guardian.
Maybe I'm missing a crucial detail, but it seems to go like this: You move the clockwork body pieces to the sculptures and repair them, the sculptures give sketches and the sculptures are permanently destroyed on full moon, someone takes sketches and leaves server, now you're no longer are able to fight the Shadow Clockwork enemies, which means you cannot get the atrium heart, which means you cannot fight the Ancient Fuelweaver, which means ruins will never regenerate nor will the Ancient Guardian in that server without admin console commands.
Remedy for this is to mark clockwork sketches as important items like chester eyebone, so that they cannot leave the server and cannot be destroyed. Krampus can steal the sketches and leave with them, and meteors can destroy sketches, so that should be changed as well.