Oh, that is supposed to happen. It has on both my Japanese and American versions, everytime I look hard enough. Quite simply, I believe it is a "second chance" thing, allowing you to catch a Pokemon you missed the day before, but at a much lower encounter rate. And yeah, they have low encounter rates to begin with. Also, both the new Pokemon for the day and the previous day's Pokemon will appear (and again, the previous day Pokemon being rarer). Really, all it takes is time and patience, and you will find the Pokemon Mr. Backlot had his butler put in his garden.