Do you mean in your app drawer? Not knowing what device you have it's difficult to say for sure. I know with Samsung if you put an app icon in a folder it won't show up in your app drawer anymore. You can use the search feature, depending on your device, on the top of your app drawer to search for apps or you can search your folders. Without more information, like what device, which settings/settings for what, there's not a lot more advice I can give.
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