Ownership:
When you create original content, the copyright is yours. You are the legal owner of the video.
License:
When you upload the video, you are granting TikTok a license to use it. This license allows TikTok to share, distribute, and even use your video in advertisements, but it doesn't transfer ownership of the copyright to them.
I think whoever originally captioned that video is going to be in a lot of trouble.