My AWS S3 bucket data not available suddenly without deleting.

Your data could not be lost due to hardware failure because data S3 redundantly store objects on multiple devices across a minimum of three Availability Zones in an AWS Region https://docs.aws.amazon.com/AmazonS3/latest/userguide/DataDurability.html

You can check Cloudtrail for the event of Deleting objects from S3 https://docs.aws.amazon.com/AmazonS3/latest/userguide/cloudtrail-logging-s3-info.html#cloudtrail-object-level-tracking

to protect you object from unintentional deleting you can use S3 versioning https://docs.aws.amazon.com/AmazonS3/latest/userguide/Versioning.html

or use MFA to avoid intentional object removal https://docs.aws.amazon.com/AmazonS3/latest/userguide/MultiFactorAuthenticationDelete.html

Hello,

As you have tagged your question with S3 Glacier, most likely, you are referring to the fact that you cannot retrieve your data immediately. To retrieve data from an Archive Storage class, you need to request the data first.

https://docs.aws.amazon.com/AmazonS3/latest/userguide/restoring-objects-retrieval-options.html

Also, maybe you have enabled lifecycle configuration, which may have deleted the data. In that case, you cannot get the data back if you have not enabled versioning.

If you have chosen the RRS storage class, which offers very low durability, data might get lost due to hardware failure.