Did you try to suggest by the common name or the Latin name? It's highly unlikely that the app would have all the common names of all the plants. Even the common name "ghost fern" refers to a few different plants. Most commonly in the ornamental plant trade it refers to a hybrid variety called Athyrium x hybrida 'Ghost'

The other major issue with ornamental plants is that they're often selected for very particular physiological characteristics. This often leads to plants that visually look very different from their wild ancestor but are still extremely closely genetically related. If you've ever had a variety of a plant with variegated leaves for example, you'll probably trip apps like these up a lot. It's simply too difficult to keep up with all the new ornamentals being bred every year. The data just doesn't exist and they're quite often weird hybrids with uncertain phylogenetics anyways