Velo code for the button is missing on the duplicated page. But the button is still working without code.

Hi there, I have written some code using Velo on a page to make it functional. Then I have duplicated that page. But I can see some part of my code is missing on the duplicated page. That missing code was for a button click. But the button is still working magically on the duplicated page. I am wondering, where is the code snippet for the button? How is the button still working without code?
Thank you.