
This gentleman let me observe for a few minutes, then he untied his rope and swam away. If you start watching closely near the end of the video, at about 6:20, you can see changes happening to the stalk just below his body. Soon after that he just lets go and leaves that stalk behind. Scrub the video back and forth over that part and you can see how he does it. For some reason, I always thought they would take the stalk with them, after all, it's part of their body.
Here's a video of a Vorticella I recorded just yesterday.
Before detaching...

Just as he let's go...
