The description for Shen's Q - Twilight Assault does not state that his next 3 attacks will restore Energy with each strike. I think that is an important facet of the skill and that having hidden mechanics like that is quite a blunder.
It's not mentioned in Shen's Q tooltip because it's actually not part of the ability.
If you read the tooltip for Shen's E, you will see that there's a passive component of the ability that gives you energy back when you deal damage to enemies with your abilities (Q and E, your damaging abilities).
You don't get energy back for damaging enemies with Q until you have leveled up E. The energy return mechanic is on the E skill.
