How to use std::find in a loop

I want to fill a vector named firstApp with some informations(id,position(x,y),frameNumber).So I make a condition to avoid filling the vector with existing informations.

for (int idxCurrent = 0; idxCurrent < nOfPedcurrFrame ;  idxCurrent++) 
        {


                if(nOfPedprevFrame == 0)
            {
                CurrentId=frames[frameNumber].GetPedest()[idxCurrent].GetID();  

                FA=FirstAppear(frames,CurrentId,idxCurrent);

                 FirstPosition=frames[FA].GetPedest()[idxCurrent].GetPosition();

                f.SetFrameNumber(FA);
                f.SetFirstPosition(FirstPosition);
                f.SetFId(CurrentId);


                if(firstApp.size() !=0 ){


                    p=std::find(firstApp.begin(),firstApp.end(),f);
                    std::cout << *p<< endl;


                    if(p == firstApp.end()){
                        firstApp.push_back(f);

                    }
                }
                else
                {

                    firstApp.push_back(f);

                }


                f.~FirstAppearance();
                 }
   }

I use std::find to search if f exists in my vector to fill it on.But when I compile my program I got that p had such value the first value of f along the life of my program.Can any one tell me why std::find didn't update the value of f with the new value?? the output of *p is:

1 263 138 0
1 263 138 0
1 263 138 0
1 263 138 0
1 263 138 0