ASK help about I-94

Dear friends, I am asking help about my parents' I-94 forms.
They came to visit us on July 8th. However, the officer at the airport didn't take back the upper portion of their I-94 forms and didn't stamp the period of duration on their passport. I worry that there will be no entry record.But my parents told me that the officer did enter something into the computer.

Does nayone have the same situation? What should I do?

Any help is appreciated.