vector of Objects having pointer of Object

Don't use pointers in the first place, there is not need here. The problem was caused by the fact that you were trying to add a Object* to a vector of Object (not to mention the fast-ticket to UB-land when dereferencing an uninitialized pointer). Here's the fixed code:

{
    Object myObject;
    std::vector<Object> stack;


    stuffHappensInObject(myObject);
    stack.push_back(myObject);

    if(IclickLoadLast){
        myObject = stack.at(stack.size() - 1);
    }
}

I've also changed size to stack.size() which is a valid method of std::vector that you can use. Also, take a look at std::stack which provides more stack-like operations:

{
    Object myObject;
    std::stack stack;


    stuffHappensInObject(myObject);
    stack.push(myObject);

    if(IclickLoadLast){
        myObject = stack.top();
    }
}

In both cases, if you are using C++11, I suggest you to use std::vector::emplace_back or std::stack::emplace instead of push_back and push.

Couple of issues:

This will not work:

stack.push_back(myObject);

because myObject has a type of Object* while the stack takes of objects of type Object. Please notice the slight difference in type. I am not sure why you are even using pointers (not enough context).

But there is another major problem:
Here you de-reference an uninitialized pointer. The result is undefined behavior.

Object* myObject;                  // No value defined (so it is random)
stuffHappensInObject(*myObject);   // De-referencing (the *) on an uninitialized pointer.