Passing 2d Vector by Reference, Changes Not Persisting - c++

Question

So in my program, I'm using polymorphism, which could also explain some of the issues that I'm having.
This is my pure abstract class:
class Event {
public:
Event();
~Event();
virtual int returnType();
};
Then I have a room class that sets events to a particular room:
class Room {
private:
Event * e;
bool player = false;
bool bEvent = false;
public:
Room();
~Room();
Event * getEvent();
void setEvent(Event *);
bool getPlayer();
void setPlayer(bool);
bool getBoolEvent();
void setBoolEvent(bool);
};
And here are my function definitions:
Event * Room::getEvent() {
return e;
}
void Room::setEvent(Event * n) {
e = n;
}
bool Room::getPlayer() {
return player;
}
void Room::setPlayer(bool p) {
player = p;
}
bool Room::getBoolEvent() {
return bEvent;
}
void Room::setBoolEvent(bool b) {
bEvent = b;
}
Here is my bats class which is a derived class from event: The functions are the same, so here are the function definitions:
int Bats::returnType() {
return 1;
}
So in my program, I am using a 2d vector of Rooms, and then assigning events to these rooms via polymorphism. The problem is that I don't think the changes are persisting, at least with the polymorphism, even when passing by reference.
Here is the function where I am setting the bat event to a certain room in the 2d vector:
vector<vector<Room>> Game::setEvents(vector<vector<Room>> &grid) {
Bats b1;
Event * eb1 = &b1;
//Set player
int r1 = rand()%gridSize;
int r2 = rand()%gridSize;
grid[r1][r2].setPlayer(true);
//Set bats
grid[0][0].setBoolEvent(true);
grid[0][0].setEvent(eb1);
cout << "Function example: " << grid[0][0].getEvent()->returnType() << endl;
return grid;
}
As an output I get Function example: 1;
However, when we move into the main (in this case Game::play()) function, these changes don't hold.
void Game::play() {
srand(time(NULL));
//Create vector
vector<vector<Room>> grid;
//Fill vector
fillGrid(grid);
//Set player and events
grid = setEvents(grid);
for (int i = 0; i < gridSize; i++) {
for (int j = 0; j < gridSize; j++) {
if (grid[i][j].getBoolEvent() == true) {
cout << i << " " << j << endl;
cout << grid[i][j].getEvent()->returnType() << endl;
}
}
}
}
As an output I get 0 0 and then a seg fault.
Although the boolEvent is still true, for some reason I get a segmentation fault when trying to call returnType(), even though it worked in the setEvents() function. What am I doing wrong with polymorphism?