There is no hose down contained by the toilet reservoir or the toilet. Why is this? The toilet was working fine in the morning and not a soul...

The toilet was working fine in the morning and not a soul used it, but there was no hose down that night.
The cistern flapper is not working properly and allows the water contained by the tank to escape into the bowl. The tank top up tube may be clogged or broken. The main water supply flash has been closed. hose down shut off or waterline plugged up...
There could be a few things wrong.some of the most common are

Is the rubber stopper working in your reservoir? This is a piece that allows water to flow to the bowl. I know because I had to replace mine surrounded by my toilet. I am not a plumber so it is fairly easy to do.

Though you would probably hear hose running all the time if the stopper/plunger is broken. Water would continue to riddle in the tank but run out...

Another problem is if the river is turned off to your toilet. If someone flushed it at night and it only never filled back up.

You can buy toilet kit at Home Depot or even Walmart. They have instructions...I did my own. But if it is something more complicated call a plumber.
Answers:    hmmmmm...probably need to replace the shut stale valve at the wall. or the ball-cock valve inside the toilet container is stuck closed. the wall valve is probably fine though as it's open and if not a soul has closed it, it should be open, (unless it's gotten clogged.). i bet the spout inside the tank is stuck closed. you can get a replacement tackle for the inside gutts of the tank for about 12 bux. read and follow adjectives instructions.
The ball-cock is probably stuck within the 'full' position.
Lift the toilet cystern lid and tap the ball. This will allow it to drop into the 'empty' position and usually does the trick.
If not, the ball-cock itself is blocked and may inevitability changing. good luck.
Is your toilet leak? Check for water on the floor, lots of it. Maybe the plug inside isn't sitting on the hole very ably, check that. Is the water going to the toilet turned on?

If your toilet is making a noise similar to it is filling up but there is no marine, then the water is getting out somewhere. If it si not making any pandemonium, the water might not be on.

Of course, the insides could be clogged or broken as well.
is your water on.