Hi
check out getdeletedfilesback.com for good advice and info on how to recover deleted files. Also what not to do... basically the lost data is probably still recoverable until the file system decides to write something new on top of what it sees as freespace (which contains your lost data). dont use the device to find an answer - use a different system to find and then run any software to recover the missing data...
Where are you getting that statistic from? Do you mean you recover 25% of the data sometimes or all the time, or do you mean you recover 100% of the data 25% of the time?