Know status of B1/B2 visitor visa

Hello everyone.

I need guidance on how to know if the stamped visa on my parents visa(Visitor), has been cancelled or not. Background - they were in US during COVID and extended their stay and stayed for around 9
months.They filed for timely extension but by the time the biometric appointment was scheduled they had left already. And after around 2 years from the initial date of filing extension, their extension applications have been denied. My question is how can I know if the visa itself was cancelled or not, just to prevent them from POE hassles.

Thank you!