Cannot Delete S3 Bucket even though the IAM user as S3FullAccess policy
Solution 1:
Bucket names must be unique within a partition. A partition is a grouping of Regions. AWS currently has three partitions: aws (Standard Regions), aws-cn (China Regions), and aws-us-gov (AWS GovCloud [US] Regions).
From the Rules for bucket naming. Most likely a bucket with that name was created by a different account not under your control. That is why it doesn't show up. AFAIK there is no other way to resolve that than choosing a different name for your bucket.