This was a short story or novella I read in the 1980s when I was a teenager. I read this in the United States. I'm guessing the story was written in the 1970s. I think I read this as part of a paperback anthology, probably a "Best of <author>" or "Best of <year>" collection. (I only say that because I remember my family had a lot of those "best of" anthologies around the house at that time, most of them from the 1970s, and most of the other science fiction I read at the time was from a small number of favorite authors. It definitely wasn't written by one of my favorite authors, because I would have remembered who wrote it if it was.) The story was written in the manner of a historical account, with the main focus on descriptions of events. There was comparatively little dialog or character development.
The story was about a single amoeba-like creature that was so huge its body filled all of the oceans of its planet. It was the only living thing on the planet. It was discovered by a lone man whose spacecraft crashed there. The creature was highly intelligent, and was able to communicate telepathically with the human. It quickly became clear that the creature had never had contact with another intelligent being before. It was very friendly, but it had very little knowledge of much of anything, because it had lived in isolation all its life. By reading the man's mind, it was able to learn how to utilize new technologies very quickly. It was able to create anything the man asked for by reading his mind and building the machinery that was needed. It eventually started coming up with new technologies on its own.
When the human government found out about this creature, they were worried it might learn so much technology it could become a threat to humanity. They decided to keep the creature strictly quarantined to limit how much it could learn. No human beings were allowed near the planet, except for two caretakers who were assigned to live on the planet and keep an eye on the creature. To limit how much the creature could learn from them, only caretakers with very low IQ scores were eligible for the job.
Because the human caretakers weren't very bright, they constantly made unreasonable demands of the creature, forcing it to be inventive and come up with clever ideas. For example, they wanted the creature to change the weather of the whole planet so it never rains anywhere (because they didn't like getting wet on rainy days), so the creature figured out a way to move all of the moisture on the planet into a vast, complex system of underground pipes and reservoirs. There were many other such demands. The creature continued to learn new technologies even more rapidly than before, but now it no longer needed to read human minds.
Eventually the human government decided the creature was too much of a threat. They decided to send a fleet to destroy the entire planet, and the creature with it. But when the fleet got there, the entire planet was gone. The creature had anticipated this event, and had found a way to escape along with its planet. To this day, nobody knows where it went.
What is the title of this story, and who wrote it?
This was not Stanislaw Lem's Solaris, or a sequel / prequel to it. While there are certainly many parallels, the planet-wide being in my story was much less mysterious than the one in Solaris. It was communicative and eager to please. It happily created food, shelter, machinery or anything else that any human asked for. From the point of view of the human caretakers, an assignment to this planet was a vacation in paradise. There was no mention of it creating mysterious copies of people. The creature was able to read people's thoughts, but it only used this knowledge to create things in a conventional manner (e.g. by refining raw materials into metals, using those metals to build machinery, using that machinery to build more advanced machinery, etc.)