It's true and happened back in the early 2000's. That's just one incident that happened with David Rudman, who at the time was working on a show idea. This is from the mouth of Rudman himself, I just know what I heard.
But let's stick to the topic which is Steve. Steve has a personal and private life as well, and it's really no ones business what happened to Steve Whitmire. I assure you all he is alive and well, but sometimes things come up just like with anyone else.
Artie did a terrific job for his first live appearance as Kermit, and in time will blossom into the Muppet family just beautifully. He has Jim's tone, and that's all you need to craft Kermit into the calm and collective sole that he really is.