Laravel：无法检索上传到存储的旧文件

I have problem regarding deleted files to my storage.

Why It happens to my production laravel project after a long weeks the uploaded files from the storage is deleted and can't view it to the storage and to my public storage.

This happen already almost 5 times, and I don't know which is wrong. The server or my codes. I don't know where to configure it out.. that happens to my live website... I hope someone can help me to solve the problem this..

Centos 7 is our server

Only the uploaded file is in there however the old is gone.

1. All images removed
2. All pdf files removed

Can I have your suggestion to find out what's going on to the project..?