How do we know if our petition was really filed or not?

What if the employer/lawyer never filed the application and lies that my application was rejected? Is there any unique number on each petition filed? The computer algorithm which selects the applications by lottery needs a number to scan the petition so what is that number does anyone know?

As per my observations, this doubt comes only when someone PAYS the employer/lawyer/consultancy for filing H-1B petitions and due to trust deficit.

Anyways, Yes, there will be unique acknowledgement number given to each applications files with USCIS. But only your employer/lawyer/consultancy will have this and it’s upto them whether they share it with you or not.

The same answer holds true for your second question as well. If you have doubt that your application was never filed, ask your employer/lawyer to share the courier/post received from USCIS upon rejection.