Also, be sure the search by Zip Code (only), not by address or by name of region.

There's one restaurant less than a mile from me which doesn't show up in a 1-, 3-, or 5- mile radius search around my home address, because they have a weird address something like 11251-53 (because techincally they have two entrances with two consective street numbers). This confuses the address search into thinking it's clear across town. But if I search on my zip code (they're in the same zip code as me), it finds it just fine.

Meanwhile, I've occasionally seen cases of a restaurant miscategorized into the wrong region (when it wasn't even near the border between two regions!), so again a restaurant could particpate but not be found under a region search just because someone put it in the wrong region. (Apparently the regions are not done automatically by zip code!)

Thus in my experience, a zip code search is a bit more likely to make restaurants show up even if they're not showing up in other types of searches.