Apps store user created/added data in a number of ways... which makes this unlikely to be answered on this board.
IF you're lucky you may just need to set user info again in the Apps prefs: which could be in Settings App under Magic Piano, or within the app itself.
If that doesn't work your best off getting info from the DEV to find out how/where it stores info. Not knowing "magic piano" I don't even know what you mean by shared...(or if you're referring to home sharing) or location.
The devs support site is available in the Apple Store on the Apps Page.
Sorry can't be more helpful. Hope you find a solution.