It wasn't Sandry

Sandry felt her cheeks start to go red, but something wasn't right. Or wasn't wrong, rather. She had split her trousers before, and was familiar with the horrific feeling of her trouser seat parting, but she had not felt that this time. She looked to the side, and saw that Robyn had bent over at the same time to grab at the stopwatch. And Robyn's face was turning very red.

"Did you just...?" Sandry began.

"I did." Robyn gulped, she slowly straightened up. "How bad is it?"

Robyn turned her back to Sandry, showing her where the seat of her trousers had been. Now the seam was parted right up the back, ragged edges pulled wide apart to show a lot of Robyn's bare backside, and just a tiny bit of white thong.

"It's, er, it's pretty bad." Sandry laughed.