Do not despair if you drop a valuable earring down the sink. Once a light, smooth item like an earring hits a slick, sloped vessel like a sink, it's a quick trip to the bottom and into the drain. Only someone with super-fast reflexes would be able to catch an earring while it is still in the sink. Fortunately, if you can work on getting the earring back before anyone else runs water in the sink, you stand a good chance of getting your earring out of the drain.
Take the sink out of commission. If you have roommates or children, or if anyone else uses the sink that you dropped your earring into, prevent them from using the sink while you work on it. If you drop your earring when you are in a rush to get somewhere and will not have time to retrieve it right away, consider making an "X" over the sink with tape to remind everyone in the household that there's an earring in the drain. When you are ready to get your earring back, place a towel or washcloth in the sink to prevent anything else from falling through the drain while you are working. Wear rubber gloves to protect your hands from foul water.
Locate the p-trap among the plumbing pipes under the sink. The p-trap is a piece of curved pipe that sits at the lowest point in the plumbing configuration. It joins the drain pipe that descends from the sink drain with the drain pipe that carries the water out to the sewer or septic system. It is sometimes called the "wedding ring trap" because it can prevent a ring -- or an earring -- from being washed away. The p-trap is easy to locate on a pedestal or other wall-mounted sink. If there is a vanity or base cabinet that surrounds the plumbing, shine the flashlight beam on the pipes underneath the sink to identify the p-trap. Once you have identified the p-trap, place a bucket or tub directly beneath it to collect any water that may drip during the project.
Remove the p-trap by loosening the fittings that hold it to straight pipe at either end. Some plastic fittings are molded with finger grips so the fitting can be loosened by hand. In that case, grasp the fitting and turn it to the left until it loosens enough that you can pull the p-trap away from the pipe. If the fitting is steel or copper, use a pipe wrench to loosen the fitting by turning it to the left. After you have loosened fittings at both ends of the p-trap, gently remove the p-trap from the drain pipe and place it on the towel in the sink. Set aside any rubber washers or o-rings that fell out during the disassembly process.
Empty the contents of the p-trap onto the towel that you placed in the sink before you began the project. Your earring should drop out onto the towel because the bend in the p-trap should have caught it when it fell. The towel will prevent the earring, and any other valuable items that were stuck in the p-trap, from dropping down the drain again. If your earring was not in the p-trap, check the drain directly beneath the sink to see if your earring has gotten stuck in an accumulation of hair or other debris. Use the flexible auger to ream out the p-trap and the drain. If you still have not found your earring, then it has probably worked its way too far down the plumbing system to be retrieved.
Examine the rubber washers that you set aside during disassembly of the p-trap. If the washers are worn, replace them with new rubber washers. Reattach the p-trap to the bottom drain pipe: set a rubber washer into the fitting, attach the p-trap, and tighten the fitting by turning it to the right. Repeat the same process for the top drain pipe. Before you remove the bucket, turn on the water to test the connections. Tighten the fittings until no water drips at the joints.