JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
If you mean the changes you've made in the form are lost, you can simply revert it back in the form revision history. Here's our guide for that: http://www.jotform.com/help/294-How-to-View-Form-Revision-History.
And here are some factors that are causing this problem in the form:
a. Editing the form into multiple windows/browsers.
b. Closing the form builder while autosave is running.
If the issue persists even if you're not doing these two, please let us know so we can investigate further. If possible, let us know what are the actions that you've made in the form builder before the issue happens.