Retrieve an Item That Was Flushed Down a Toilet

Depending on where in the toilet the item is stuck, you may have to remove the entire toilet from the floor to access the stuck item.

Steps

Obtain a plumbers snake. It's a coil of wire that you can unwind to clear stuck drains. If you don't have access to one, get a wire coat hanger and unwind it with a pair of pliers so you have a long piece of stiff wire.
Push the snake or wire into the bowl and if possible, grab onto the object and try to pull it up and out. If you can't grab onto it, don't push it further down or you might obstruct the waste pipe.

If the above doesn't work, you'll have to remove the toilet. At the base of the toilet, there are metal bolts on each side held on with metal nuts that hold the toilet to the floor.(the bolts are hidden under removable caps)
Shut the water supply off to the toilet; there should be a shut-off valve under or behind the toilet where the water supply for the toilet exits the wall/floor. If there is not, or the valve is seized, shut off the water to the entire house. The main water shut off should be in your basement where the water from the city enters your home.
Flush the toilet to drain the tank. If there is any residue left, clean it out with a sponge. You will need to drain the bowl with a cup and a sponge to remove all the water.
Once the tank and bowl are free of water, use a pair of pliers to loosen and remove the bolts holding the toilet to the floor.
Having someone assist you, lift the toilet from the floor. Lift it from the bowl, not the tank. (There will be some wax residue on the bottom of the bowl and the floor from the wax seal.)
Place the toilet on its side so that you'll have access to the bottom
Using the snake or coat hanger, retrieve the item from the bowl.
Once the item is removed, reinstall the toilet (in the reverse order it was removed), turn the water supply back on to the toilet and allow it to fill.

If you had to remove the toilet from the floor, you'll have to replace the wax seal. Any hardware or home improvement store sells the wax seals for toilets; they're inexpensive and should be replaced any time you have to remove a toilet to work on the floor, paint, etc. The wax seal makes a watertight seal between the toilet and the waste pipe. Take a spatula and remove any old wax that still remains on the bottom of the toilet and on the flange in the floor before you install the new seal.

If the toilet is removed from the floor, put a rag into the waste pipe to prevent noxious and explosive sewer gases from entering your home. Always remember to remove the rag when you reattach the toilet.
Always tighten bolts on the toilet to hand tightness, or you may crack the porcelain. Once the bolts are hand-tight, turn 1/4 turn with pliers.
Move the toilet with caution. The porcelain bowl and tank are easily cracked/damaged.
When you reset the toilet, push it gently onto the wax seal and jiggle it gently to ensure a proper seal. You can allow the toilet to compress the seal with its own weight or you can sit on the toilet.