If I am remembering this correctly,I believe that a scan logfile isn't produced from the scheduled scan.However,I can't find anything about that on the forum,and memory alone isn't trustworthy enough on that.If it does show that a scan ran last month in the scheduler tab,that should be trustworthy.
But to be more certain,you could follow these instructions to edit the system scan task to a convenient time and date when you can watch for the scheduled scan.
https://www.safer-networking.org/faq...a-system-scan/
If you've got a time when you aren't busy,temporarily setting the system scan to run the scan in a couple minutes works well(using that day's date,of course.)