Sad to say, Facebook has numerous bugs and arguable features in its App Directory, and the chance of finding an app in the directory, without knowing its exact name, is very hard.
The most serious bug is that currently it’s impossible to enter an app description nor any image to a directory profile. That has caused PalFinder to get stuck in limbo somewhere between being approved (which it is) and not being visible under any category in the directory.
Facebook doesn’t answer any of the support complaints, and there are several on the same topic, so it’s anyone’s guess when this will be fixed.
The only way to find PalFinder in the directory at the moment is to search specifically for ‘palfinder’.