Dude this happened to me the other morning at like 5 am....I was like holy shit. ..I left twice and came back and it was like that. I said I must be hallucinating and went back to bed.
This happened to me yesterday. There weren't any players or NPC's that I could find. After a minute or two I paused the game to look at something and when I unpaused everything was back, including players.
Bad connection to servers or no available servers will load the tower on your own console. But the NPC's are still loaded from servers. Sometimes you'll be the only guardian there, free to shop without muppets trying to dance with you or beg you to raid, and sometimes its you. Just you.
"Ro-nry, I'm so ro-nry"
Thats happened to me a few times.
I also had "Ghost Town Crucible" match... that was weird.
And I also had "Ghost Town Universe" on a couple occasions: my ship is just endlessly flying through space (I think I let it run for about 20 or 30 minutes just to see how long it would go one for... it didn't stop).