Laguage key is not displaing

Language key was displaying properly before but when I restore data, it does not displaying anything.

Please see attached image.

I know it is not able to add any language key with <bx_text:_sample />. So I have adding code into database (_sample_main)
It was showing just fine but when I was restore for some reason, it is disappearing.

If there is any of you know how to solve this problem, please kindly let me know.

Check if it really exist and recompile lang.

I have checked following tables and it is existing.
sys_localization_keys
sys_localization_languages
sys_localization_strings

So I have no idea why it is disappeared.

Please explain in more details what you mean by "when I restore data" ?