Thank you for the pictures, that cleared up the Cave of Sighs guard for me. 
As for the Observatory, its hard to tell if the temple guard was in there after rewatching the run. To me though, the Observatory seems like the only logical place for that last temple guard. Unless there was another alternate route in the Treasure Room to the Holes of Python. But that doesn't make sense though because the Shrine door was unlocked anyways. Its a really weird layout and I wish the producers would've revealed the temple guard locations at the end of every temple run. That would've been pretty neat.
I doubt that there would have been an alternate route through the Holes of Python. The door was clearly closed from the Throne Room, and there was no need for the Treasure Room to be unlocked to the Holes of Python since the Shrine opened directly. Not only does that narrow down the possible final temple guard location down to the Observatory, there was also the glint of a headdress in the Observatory.
There were three guard costumes used throughout all of Season 1: one with a gold mask and a necklace with several golden pendants; one with a black mask and a leopard-print shawl; and one with a green mask and a feathery red and green headdress. All three guards were encountered in the Medal of Sir Edmund Hillary run, and all had relatively clear screenshots (photos courtesy video posted on youtube.com by ChargerTheWolf):
Some of the guards tended to reside in the same rooms, as Micheal Lupin disclosed during an interview regarding being a temple guard during Season 3. As shown in the bottom left photo in the lower set of photos, in Season 1, the gold-masked guard was always housed in the Cave of Sighs. That photo was taken from the "Lawrence of Arabia's Headdress" run.
However, in the "Silk Ladder" that guard was placed in the Throne Room (upper left). If a guard were to have been residing in the Cave of Sighs during this run, that guard would have been stationed there; however, since that guard was in the Throne Room, the Cave of Sighs was clear. The other guard in "Silk Ladder" run (upper right) was the black-masked guard. The only guard left was the green-masked guard.
The bottom right photo is a very clear, up-close shot of this guard from the "Codebook of Mata Hari" run. As you can see, this guard had a very distinct, shiny, gold pendant-shaped emblem on his headdress, surrounded by green and red feathers. If you compare the other, earlier photo of the Observatory from the "Silk Ladder" run, the glint could very easily have been from that emblem. Additionally, there is a faint, dark shadow around the glint that could have been from the feathers on the headdress.