1) This situation indeed seems problematic from a security perspective. In general, it's against the security policies of most airlines, as well as international aviation regulations, to allow a checked bag to fly on a plane without the passenger who checked it. This rule was implemented primarily to prevent the potential risk of someone checking a bag with a dangerous item and then not getting on the flight. However, there can be some exceptions, such as when a passenger is on a connecting flight and their bags are checked through to the final destination, or when a passenger becomes ill and cannot board the flight.

2) As for compensation, it would largely depend on the specific airline's policies and the circumstances around why the flight left early. If the airline was clearly at fault (e.g., the flight left well ahead of the scheduled departure time and there was no communication to passengers about this), you might be able to make a case for compensation. However, you would need to contact the airline directly, file a complaint, and provide as much evidence as possible.

Remember to check the terms and conditions or the contract of carriage of the airline your son was flying with. Most airlines have a 'Contract of Carriage' available online which will detail their liabilities and responsibilities in situations like this.

In both cases, the most important first step is to contact the airline directly and explain the situation. They should be able to provide some clarity about what happened and how they plan to resolve it. In the meantime, you might also want to file a complaint with the appropriate aviation authority, such as the Federal Aviation Administration (FAA) or the Department of Transportation (DOT) in the United States, or the corresponding agency in other countries.

Regarding the other people left behind, it seems that there might have been a significant operational error if multiple people were left behind and the flight left early. Each person should separately file a complaint and ask for compensation. The strength of the claim may increase if there is clear evidence that multiple passengers experienced the same issue.