S3 deletes files by itself

Hi,

Have you configured a lifecycle rule to automatically expire objects older than a certain number of days? You can review why an S3 object has been deleted though server access logs or AWS CloudTrail data events, but both had to be previously enabled on the bucket or CloudTrail.

Follow below article and verify lifecycle settings https://s3browser.com/amazon-s3-object-expiration.aspx#:~:text=Amazon%20S3%20Object%20Expiration%20Overview,-Recently%20Amazon%20S3&text=The%20prefix%20(e.g.%20%22logs%2F,expiration%20rules%20for%20different%20prefixes.

i didn't enable any lifecycle settings