Thibault is the first WNBA coach to reach that milestone. Sparks coach Brian Agler is second all-time with 264.
Toliver, who hit all of her 13 free-throw attempts, made two foul shots to spark an 8-2 spurt that gave the Mystics a 74-66 with two minutes left after a jumper by Natasha Cloud. Chelsea Gray hit a 3-pointer to pull the Sparks within five with 1:18 remaining, but Washington made 9 of 10 free throws from there to seal it.
Gray led Los Angeles (12-8) with 23 points and Nneka Ogwumike had 22 points, 13 rebounds and five assists. The Sparks have lost five of their last six.
The Mystics shot just 41 percent, including 1 of 16 from 3-point range, but made 32-of-35 free throws.