According to Piccard-Lindelof Theorem, there exists a solution for every Initial Value Problem (under some conditions like Lipschitz, etc.) and that solution is unique. However, when we say that the solution is unique, we mean that it is unique GIVEN some interval, right?
Because if not suppose f: (1,2) --> R is a solution, then g: (1.5,2) ---> R is also a solution and so the solution would not be unique.