To restore H&S without an hs.app you must do the following:
1 - Uninstall H&S (FBI) with another installation of FBI (cia or 3dsx version). The title you should uninstall is the one with the product code CTR-N-HAC? where the ? corresponds to the region of your 3DS. It'll be one of those red titles on the titles list.
2 - Download the following title using
3DNUS: 0004001020021300 v2051 (US version) or 0004001020022300 v3077 (EU version) and pack it as CIA. If you're using a New 3DS the version should be v1 in both cases.
3 - Install the CIA you downloaded using FBI.
Alternatively you could just remove it with FBI (step 1) and update your 3DS skipping step 2 and 3.
This should fix your H&S app. However, it'll probably still appear as FBI in your Activity Log. To fix this you should clear the shared app icon cache.