Explore for any given day doesn't become "official" until the following day at midnight. Days in Explore are counted using PST (GMT-8) (because that's Flickr time).
I know people like to look at Explore for the current day but there's a reason Flickr doesn't link to the current day's Explore (only yesterday's and older). The results don't become "official" until the day ends when all of the photos for that day can be evaluated fairly. Otherwise it's like running a race but letting some people start early. Rankings don't "count" until the very last photo of the day is uploaded (because that one could be #1 for the day).
The Flickr API, which is what Scout uses to get Explore data, doesn't even give valid data for the current day. So Scout waits until midnight when the results become official. This photo was never dropped because it was never officially in Explore for the 17th.
Sorry.