Actually, press F1, and then F9=Display message details, on the DSPLOG 
entry which states
  05:34:31 PWRDWNSYS issued, restart=(*YES *FULL).
You should see something like
From job
  User .
  Number
That's the job you need to get the job log from.
We use a utility to scan message files and I didn't see any with the 
format above.  I checked
QSYS/QCPFMSG
QBRM/Q1AMSGF
QBRM/Q1QPMPT
Honestly, us on the list are trying to see if you are "mistaken" as to 
whether or not RESTART(*YES) was specified.
Getting past that...
Don't you have a UPS on this machine?  Is the date and time on the UPS 
somewhat accurate?  Does the UPS log a power outage around for that time 
period?  Most UPS I've seen have a menu on the front that you can page 
through to view the alarms.
Next step is to study the utilities the i has for handling UPS signals, 
how to hook up the signal cable and how to use the system values 
effectively for an attached UPS.
You could also tell them to do a 
DSPLOG PERIOD((053431) (091210)) OUTPUT(*PRINT)
Then show them how to use iNav to drag a spool file to their desktop and 
have them email that to you.  You should see power failure messages.
See also:
WRKSYSVAL QABNORMSW
WRKSYSVAL QIPLSTS
Rob Berendt
As an Amazon Associate we earn from qualifying purchases.