So it did happen but Facebook didn’t shut the experiment down, but rather they changed the experiment parameters so the bots would stop using their own language.
The article I read said they shutdown the experiment. So, the article wasn’t 100% accurate and the article I read was published in late 2018 or early 2019. So, it was either recycled news or the experiment lasted several years before the bots made up their own language. As the experiment was started in 2017, according to the fact check article linked above.