4. Goku, heading out from the Red Ribbon Army's headquarters, has six of the Dragon Balls. Why, according to Bulma, is it likely the Dragon Ball isn't appearing on the Dragon Radar?
From Quiz Dragon Ball - Fortuneteller Baba Saga
Answer:
It's been eaten by a creature
At the Red Ribbon Army Headquarters, Goku faces off against Black, the final remaining leader stationed in a giant mech. Fortunately, Goku is able to evade taking a final large blast and stop Black before he escapes, bringing the mech down and putting an end to the Red Ribbon Army once and for all.
Bulma, Yamcha, and the others arrive moments too late for the battle, but not too soon to reunite with their friend. Goku, now with six Dragon Balls, says that he'll still continue to search for the final ball, but it won't show up on the Dragon Radar. Bulma assumes that the problem lays with the hiding spot of the ball; they won't be able to find it as is. On Master Roshi's recommendation, Goku decides to visit the mysterious Fortuneteller Baba for guidance, but not before gathering Upa for the quest, getting a new outfit, and flying along with Yamcha, Puar, and Krillin in tow.