I recently had the same thing happen with 2 OnTrac deliveries from
Nordstrom and Sephora (I highly don't recommend OnTrac). I was home all day with a yappy dog who barks anytime the wind blows, yet nothing had arrived when at 9pm the packages suddenly switched to delivered.
After a lot of back and forth with their headquarters office, I discovered that this sometimes happens when the driver completes their route and returns the delivery vehicle. Even if the item is still on the truck and hasn't been delivered, apparently the route completion triggers all scheduled packages to display as delivered until a manual entry is made. I wonder if UPS has a similar system in place, as your situation sounds exactly like mine. (Except my packages didn't come the next day either, because as I said, OnTrac blows).
Good luck to OP for a good resolution.