How to find account behind ip address 15.197.142.173

There's a bunch of places you could have a public IPs defined. Have you checked for example EC2 instances, elastic IPs, load balancers, CloudFront, maybe even Global Accelerator? Also could it possibly be in a different region that you expect? If you have a lot of accounts you could script your checks, for example using the CLI to check EC2 instances with server-side filtering: aws ec2 describe-instances --filters Name=ip-address,Values=15.197.142.173