Some apps does not shows through market app if that application contains market filter options like the one that is mentioned on the link below: http://developer.android.com/guide/appendix/market-filters.html.
<supports-screens android:resizeable=["true"| "false"]
android:smallScreens=["true" | "false"]
android:normalScreens=["true" | "false"]
android:largeScreens=["true" | "false"]
android:xlargeScreens=["true" | "false"]
android:anyDensity=["true" | "false"]
android:requiresSmallestWidthDp="integer"
android:compatibleWidthLimitDp="integer"
android:largestWidthLimitDp="integer"/>
If any one of these filter options is provided in the Android manifest.xml file then the applications will be filtered on the market app while we searching and only the device that meet required features will only be shown/listed. But on the mean time if you search through the web browser the application will be listed. Market filters, filters the app only from the Android market app and not while browsing through a browser. For an example: if an applications mainfest.xml contains :
<supports-screens android:smallScreens="false" android:normalScreens="true"
android:largeScreens="true"/>
Then that application will be shown only while we are searching from a device of screen sizes that come under normal and large. This application will not be listed if we are searching from a device that comes under small screen sizes. And if we search the same app on browser it will be listed. Kindly check if that condition is preventing the app to be listed.