Sum all the individual digits of 1-250 (e.g. 11 is 1+1 is 2). Sum all the individual digits in your string. Now you at least know the sum of the missing digits

Sum all the individual digits of 1-250 (e.g. 11 is 1+1 is 2). Sum all the individual digits in your string. Now you at least know the sum of the missing digits, and how many missing digits there are.