Lance messed it up, it's not never come back, it's never return. You need to confront him about this.
Also, I just caught a shiny Duskull in Emerald (funny enough, I hatched one in my old file, so now I have two of them!) so now I can RNG for any wild Pokemon for shininess once I find my SID. And I'll be able to get shiny Croconaw from Birch. So I've had the best 48-hour in-game period pretty much ever. GO ME