How to search installed apps
Spotlight can be slow and only returns partial results in some cases.

Solutions include:


Examining free space on the phone and deleting things so that there is about 1 GB of usable storage space.
Power down the iPhone and start it back up. Sometimes keeping a low CPU program running like stopwatch or count down timer can let the background process that updates spotlight get enough CPU time with the device awake to complete the indexing.
Uninstall the app and reinstall it.
Open a support request and they can gather diagnostic logs to determine why your spotlight database isn't updating.