Oh, better yet- to take a leaf from Dogasu's book, during the entire journey Brock was secretly concealing a pirated Dragon Radar, and at some point in between episodes, or perhaps during moments where he is not visible when Ash is gym battling or something, he was searching for the Dragon Balls, which he eventually found and used exactly twenty episodes before he came home, wishing his mother back to life. He then promptly forgot about the whole thing due to Akira Toriyama coming out of nowhere and whacking everyone repeatedly over the head with a rubber chicken for violating copyright and stealing his ideas. Thus, we have a living mother and no memory of her ever being dead! It works! *is hit by car*