In the past days I was looking for a solution and found this formula (not related with the problem I had):
=+SORT(A:A;A:A="ab c";;A:A;1)
I was curious and I tested this formula following the instruction of the guy who posted it in another forum witch where I can't remember right now.
The symbol + made the SORT function return the first cell alone that matches the criteria.
But I want to know more about this kind of customization of formulas using + and if is possible to use other operators. Is it documented?