iTunes Match is nice, but can also be a pitfall for developers due to many songs. If you want to exclude songs that are not stored on the device and therefore not available offline, take the following snippet. It also can help you to speed up your app performance.

MPMediaQuery *mediaQuery = [[MPMediaQuery alloc] init];
[mediaQuery setGroupingType: MPMediaGroupingArtist];
NSArray *queryResult =  [mediaQuery collections];
NSMutableArray *myArtists = [[NSMutableArray alloc] init];

for (MPMediaItemCollection *artist in queryResult)
{
   MPMediaItem *item = [artist representativeItem];
// Important: We don't want any iTunes Match tracks due to performance issues
// But this check only really works since iOS4.3

   NSURL *assetURL = [item valueForProperty:MPMediaItemPropertyAssetURL];

   if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"4.3"))

   {
     AVAsset *asset = [AVAsset assetWithURL:assetURL];
     if ([asset isExportable] == NO)
     {

// not stored on the device - only available in iTunes Match

      continue;
    }
  }
}

The most interesting part is the isExportable flag. If it returns NO, then the asset (song) is not stored on your device (iPhone, iPod or iPad).
Be careful: It only works since iOS 4.3
SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO is just a simple macro

#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion]
                                                        compare:v options:NSNumericSearch] != NSOrderedAscending)