DBZK Episode 27
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
"A Touch-and-Go Situation! Gohan, Protect the Four-Star Ball!" (一触即発 の ピンチ! 悟飯 よ四星球 を 守れ, Isshokusokuhatsu no Pinchi! Gohan yo Suushinchuu o Mamore) is the twenty-seventh episode in the Dragon Ball Z Kai anime.
Son Gohan found the Four-Star Ball that Vegeta had hidden earlier. Kuririn found Bulma looking for Gohan so Guru could unlock his hidden potential. He discovered that Gohan had left. On his way back to his friends, Gohan was found by Vegeta. He managed to hide the Four-Star Ball, but kept the radar in his hand. When a suspicous Vegeta asked him about it, Gohan claimed that it was a clock. After a brief conversation, Vegeta viciously kneed Gohan in the stomach and left, however, he eventually realized the radar's true purpose and also realized that the remaining Dragon Ball had been taken by Gohan. An angry Vegeta turned around and headed in the same direction as Gohan.