Russell Porter, a youngish orienteerer from British Columbia / California that was visiting town, apparently knew about this event and maps online, maybe reading about it right here on AP, and went for a walk on his own on the South Side Slopes, retracing the route of Step Trek, apparently following the orienteering map I presume he found online.
Then, all of a sudden, he saw an actual orienteering control. Peculiar, as we are now 18 days after the event. He reported it to the WPOC Facebook page. At 6:30 PM, a search party was on the premises, and sure enough, the control flag with ID "302" was indeed there.
The location was on an end of a covered footbridge going over the railroad tracks, in a thick urban setting, with daily pedestrian traffic. For this flag to be left there for 18 days, that's amazing. Maybe there is credit to be given to the written label attached to the control, "Please do NOT disturb. Property of WPOC"