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.
The data are not lost it is still in your form, but it will not show as you have replaced the fields that are associated with your submissions. You can retrieve this by reverting your form to an earlier version where all submissions were still there.
Please check this guide http://www.jotform.com/blog/95-Introducing-Form-Revisions-Never-Lose-Your-Work-Again-.