Why does the Webform disappear after changing Submit button text in Form settings?
Difficult to know what's going on based on the limited information you've provided, but it could be permissions. If you don't have permissions to view the webform then you won't see it.

The scenario you've described might occur if you are configuring the webform while logged in, then testing it while logged out (or in another browser) as an anonymous user that does not have permissions to view.