When I try to open an *.org file that I have previously created and saved, Emacs only displays the first line of the file in the buffer. I load the file with C-x C-f. I witnessed this behavior for org files only. When I open the org file with another editor (sublime, notepad, etc...) the whole data is there so the file itself seems fine. Could not find any documentation on this behavior.
This is the expected behavior: by default, org files are opened in a folded overview state. You can use TAB (bound to
org-cycle) to expand the outline tree.
If you prefer your Org files to open in an already-expanded state, you can either customize the startup behavior:
M-x customize-option org-startup-folded
Or you can control this per Org file by adding something like:
(See Visibility Cycling in the Org manual for more.)