(Not yet anyway. Just wait for a time displacement wormhole or something.)

"Well, it was when we sent you back to your own time. After you guys defeated Cell, remember?" Of course he doesn't remember! But Bulma isn't one to be careful about time-sensitive information. Instead of even worrying about the possibility of timeline corruption, she places her hands on her hips, and starts chiding him instead.

"You know, I really thought you might come back and visit us sometime. Or at least send a card and let us know how you were doing!"