As the Health app cannot be deleted from an iPhone, it's there somewhere. If it shows up when you search for it, it's still on your phone.
How many pages of icons do you have? I've forgotten exactly what the limit is but, if you have more apps than will fit on that number of pages, the others will be effectively hidden. You can still access them by searching, though.
Have you looked in all the folders on your phone?
If all else fails, you can reset your Home Screen layout by going to Settings>General>Reset>Reset Homescreen layout. Note that any folders you've created will be obliterated.