Trundle's Q does not trigger Cheap Shot

Chomp: Trundle's next basic attack bonus physical damage and slows his target by 75% for 0.1 seconds.

Cheap Shot: Basic attacks and damaging abilities deal 10 − 45 (based on level) bonus true damage to **slowed **or immobilized enemy champions.

If you didn't know, Trundle briefly slows an enemy for chomping them with his Q. This in question should proc the rune for its intended effect, which is dealing bonus true damage to a movement impaired enemy champion. Even after basic attacking after the Q, it still does not deal the damage as promised.

Though I'm not really sure if the extremely short slow duration is the issue (0.1 second) here but the way the rune is worded does not include "slows must be longer than x seconds" so I'm pretty sure it is a bug.

Don't have a clip showing the bug but you should try it in Practice Tool on a dummy, it doesn't work.