An enemy of goku in the future use earth's dragonballs to go into the past and used the earth's dragonballs of the past to get his hands on namek's dragonball and made two wishs, one was to bring pan into the past, two was to wish that videl and pan was tied up with inescapable rope with a mute gag or pan in her travels through the universe to find the black star balls got pulled into a time vortex and was sent to the past at the same time that videl found all the dragonballs but one of videl's enemys got to her first then pan appears and the villain wish upon the dragon ball to tie them both up with inescapable rope and a mute gag. It's one of those storys that happen I'll leave the choice up to you.