To find the wish tag on Pokemon Ruby all you have to do is walk around inside seafloor cavern(not the sand part, actually INSIDE the cave) and have a party full of zigzagoon(or any pokemon that knows pick up). You'll also need a pokemon that knows dive/surf to get to the cavern. Then just walk around for a while and one of them should pick something up. This method is how I got my wish tag but also can take a LONG TIME!(P.S. There are pokemon in the cavern so beat them too!)Hope this helped!!!!