Review your system audit journal, QAUDJRN. Look for T/CD entries for RMVJOBSCDE. Or look for T/ZC entries for the QDFTJOBSCD *JOBSCD object.
Both of those assume that your system is auditing appropriately. For the first, you’d be auditing commands run by users. For the second, you’d be doing object auditing for the default *JOBSCD object.
If neither of those apply, then you might get lucky by scanning joblogs at random. If you aren’t doing auditing, you can’t review audit events later.