You don't mention the amount of the bonus you were offered.
In the communication back and forth between you and the scheduler, did you agree to open an account? Did the scheduler respond and actually name a dollar amount for a bonus? Or did you just figure you would receive some undefined bonus based on the statement "you are not required to open an account, but if you do, I can pay a bonus....?" So you opened the account, put it into the report, and waited for some extra bonus money to arrive? If there was no discussion of dollar bonus amount, there was no agreement.
Was this a KSS scheduler scheduling bank shops for Reality Based? If so, this is not an unusual situation. The teller shops for this bank are very unpopular and they have difficulty getting them shopped every month. The KSS scheduler sends constant begging e-mails for someone to do the teller shops. There are frequent begging e-mails when she schedules the platform shops, saying you don't have to open an account but there will be a bonus if you do.
She gets around paying the bonuses because, unless you contact her in advance, before you do the shop, AND you tell her in advance you will open an account AND you agree on a $ figure bonus, there will be no bonus. And if forced to pay, the bonus is likely $5.