I understand that you spoke with one of our support team members over the phone and they were able to resolve this issue with you.
For future reference, the issue that you were having was that several of your sections had disappeared from the screen designer view of your custom screen. The sections could still be seen on the screen itself. The following steps were taken to resolve the issue:
1) Navigate to the Advanced options of the screen and selecting Show In Sections, as well as unchecking Show First Section To Left Of Screen
2) Saving & Closing, choosing to Publish in the process
3) Viewing the screen
4) Navigating back into the screen designer and clicking Show for all visible sections
5) Saving & Closing, choosing to Publish in the process
6) Viewing the screen
7) Navigating back into the screen designer, where all Sections were once again visible
I hope this helps.