I dreamed once that I was kidnapped.what does this dream mean?

Dreams don't always have a "meaning" behind them.
Dreams can be explained this way: Your brain is a big bowl full of emotions and thoughts. When you think of something, or feel something, it gets thrown on top of past thoughts and feelings. Dreams are basically a hand that is reaching into the bowl and pulling out these thoughts and feelings.

For instance let's say the hand pulls out fear. Horse. Green. Road. Bear. All of a sudden you're riding a horse along a road, sorrounded by the color green, and you are afraid because you are being chased by a bear. This is how your dreams work.

The more you think of something the more it will be thrown into a bowl, and the more likely you will dream about it. Also, the more recent the thought or feeling is, the more likely you will dream about it. So, if you had a dream last night about a rock awesome, relaxing vacation, you're going to want to meditate on that throughout the day to increase your chances of having a similar dream again...
Get it?