Automatic ec2 instance deletion by aws

AWS won't delete your instance, unless in specific circumstances, e.g. if it was a SPOT instance (which in your case I don't think it would have been, as you can't create a SPOT instance without knowing about).

It's possible the instance could have crashed because of an issue on the running workload, and this should leave it in a stopped state and not terminate it (unless it's part of an auto-scaling group, but again you would know that you are putting an auto-sclaing group in place).

Can you check that in the AWS Console you are looking at all EC2 instances and not just those that are running - select the option in blue and not the one in red:

Also check you are in the correct region, see the top-right corner of the AWS Console.

You can check all EC2 instances in all regions in EC2 Global View https://console.aws.amazon.com/ec2globalview/home#

As @Steve_M mentioned, AWS won't delete your instance, and a common mistake is accessing a different region than the one where you set up your EC2 instance, so using the EC2 Global View feature can help you check all your instances across all regions.

If you still can't find your EC2 instance, note that AWS CloudTrail keeps a record of any actions taken by a user, role, or AWS service for the last 90 days in each region, so you can use it to figure out how your instance was terminated. Check out the following Knowledge Center article for more information.

Just make sure your in the correct region. The console does change regions under certain circumstances. Check the Top right your in the region and account where you created the EC2