An EC2 instance, once terminated, may be available in the AWS console for a while after termination. The user can find the details about the termination from the description tab under the label State transition reason. If the instance is still running, there will be no reason listed. If the user has explicitly stopped or terminated the instance, the reason will be "User initiated shutdown".
Reference:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_InstanceStraightToTerminated.html

Explanation
Refer AWS documentation - S3 Server logs
To turn on log delivery, you provide the following logging configuration information:
* The name of the target bucket where you want Amazon S3 to save the access logs as objects. You can
* have logs delivered to any bucket that you own that is in the same Region as the source bucket, including the source bucket itself.We recommend that you save access logs in a different bucket so that you can easily manage the logs. If you choose to save access logs in the source bucket, we recommend that you specify a prefix for all log object keys so that the object names begin with a common string and the log objects are easier to identify.When your source bucket and target bucket are the same bucket, additional logs are created for the logs that are written to the bucket. This behavior might not be ideal for your use case because it could result in a small increase in your storage billing. In addition, the extra logs about logs might make it harder to find the log that you're looking for.