A phantom passenger claim in its simplest form is an injury claim from a person that was not present in a vehicle involved in a crash. It is certainly one of the more brazen ways to pursue a fraudulent injury claim by attempting to circumvent any fraud detection process and acquire a quick compensation pay out.
Identifying claims for further investigation can be as straightforward as noticing that there are more claimants than seats in a vehicle, the at-fault driver disputing the presence of a passenger, or there are photographs / video footage showing vehicle occupancy.
https://kennedyslaw.com/en/thought-leadership/blogs/fraud-blog-fundamentally-honest/navigating-the-ghostly-realm-of-a-phantom-passenger/