She hasn't lost her chance; it just appeared for a while that she had. The boat they were taking to Pacifidlog broke down, and on the way to the harbor where they could catch another one, the group got separated, with Ash and May away from Brock and Max. Ash and May got to the harbor just before the last boat of the day (which was also the last one that could get her there in time for the next day's contest) was going to leave. Ash tried to get May to go on alone, promising that he'd find Max for her, but she refused, and the boat left without her.
[spoil]In the end of the episode, they ended up getting back onto the boat that had brought them to the island, as the captain had managed to fix the engine problems.[/spoil] (highlight to see the resolution)