ALMOST surely: This has to do with your settings in the Auto-sizing section of the Appearance tab of the inspectors pallette (in layout mode). At least for me, this has been the issue when things went missing...
For the 3 (missing) icons on the left: make sure the little lock icon is set ONLY for Top and left.
Note that each element on your layout can have it's own settings.
There's a thread which describes this behaviour as a bug at: https://fmdev.filemaker.com/message/79488#79488
You indicated this is a list-view layout. Does making the LAST record the active record in the list have any affect on these footer-buttons' visibility?