It is likely that there is a filter on the 'View Settings'. You may try to 'reset' the 'view settings' to clear 'filters', if any. To restore view settings click 'View' > 'View Settings' > 'Reset Current View' > Check the results
If the issue persists, try tapping <Ctrl><6> to view the complete 'Folder List'; browse for the missing 'emails'. If it is still missing, try to 'clear and regenerate' the 'Navigation Pane' for the 'Current Profile'. To clear the 'navigation pane' settings, click 'Start icon' > Type 'outlook.exe /resetnavpane' (without quotations) in 'Search Programs and Files' text-box > Tap 'Enter' > Tap <Ctrl><6> again to view the 'Folder List' > Look for the Emails now
Hope this helps. Do reply if you have any further questions; would be glad to assist.