Changes disappeared after publishing. Why is this happening?

Most likely it happened because of a browser tab having the page opened in admin, then in another tab doing changes to that page in LC, and then saving that page in the admin (the first tab) which doesn’t hold information made to the page with the LC builder after that tab was originally opened.

If you clicked the “Publish Changes” (the main save button) and it did it’s loading animation and went away it means LC passed the data to WP, WP saved and confirmed the save. Otherwise, the alert prompt shows saying “  Something went wrong”.

It also shows the “Something went wrong” if the data you are saving is the same as the data that already exists. 

Also, please make sure to clear the website cache after making changes, if you are using any cache plugins like W3 Total Cache or Super Cache.