Latches/locks/linkage Related Problems of the 1999 Chevrolet Silverado 1500

Latches/locks/linkage problem

1999 chevy silverado. On 1/21/11 I pulled the manual release lever to release the driver's side seat and load material into the extended cab of my pickup. A plastic piece with metal components inside the track (quoted from dealer as a seat adjuster) fell out of the right side track. My driver's side seat would not and continues not to lock into place, causing me to have to drive with one foot on the floorboard, and use the other to accelerate and brake continuously. When driven, the seat freely moves forward and backward with centrifugal force. Note: the seatbelt is attached to the seat completely, not anchored to the sidewall and floor of the vehicle, so there is nothing to keep a driver from sliding all the way to the steering wheel if and when this piece fails.