Did Lewis and Clark kidnap sacagawea?

No they did not. Sacajawea was about thirteen years of age when she was bought and taken as a wife by Toussaint Charbonneau, a French trapper. She would join the Lewis and Clark expedition after her husband was interviewed to be an interpreter. Lewis and Clark (esp Clark) weren't overly impressed with his skills, but were impressed with Sacagawea who spoke Hidatsa and Shoshone. Therefore they hired Toussaint and Sacagawea naturally came along.