Okay, the sighting in Namibia occurred around 3 PM in Namibia on March 15.
As oval said, there is SW285 WDH-FRA 2130-0655(+1)
Also, before the Frankfurt flight, there are many flights throughout the day to Johannesburg.
And from Johannesburg, there are many night flights to places in Europe/Asia, such as Dubai, Frankfurt, Istanbul, London, Paris, Zurich, Abu Dubai, Munich, Cairo, Doha, Tel Aviv, and Amsterdam, all arriving in the morning.
Also looking at St. Petersburg, there are arrivals in the early morning on the 17th from Berlin, Vienna , and Istanbul, and that is it. There are multiple flights coming from Moscow to St. Petersburg, where teams could easily fly into Moscow in the morning and then take a 2 hour flight over to Saint Petersburg.
Arriving from Moscow DME in the morning of the 17th we have Tel Aviv, Minsk, Vienna, Munich, Berlin, London, Lisbon, Barcelona, and Madrid
Arriving from Moscow SVO in the morning of the 17th we have Barcelona, Paris, Istanbul, Amsterdam, Rome, Frankfurt, Munich, Budapest, Venice, Prague, Nice, Belgrade, Milan, Brussels, Vienna, London, Odessa, Cairo, and Tel Aviv.
So bottom line, we have lots of places that teams can get to on the 16th and then make it to Saint Petersburg flying out the night of the 16th and arriving the 17th. The issue is that it leaves us with no time stop somewhere, do some tasks, and have a pit stop rest. It is very very unlikely to sandwich something in there, unless there would be some sort of no rest leg/KOR/TBC somewhere.