Function not changing boolean value

Same code is working when not used as part of a function. Any ideas why? Currently using tinkercad to simulate as I'm not near my hardware at the moment incase that's related.
P.S very inefficient, yes, but that's a problem for later.

// pin declaration
// flood lighting
const int LEFT_FLOOD = 10;
const int FRONT_FLOOD = 3;
const int RIGHT_FLOOD = 4;
// emergency lighting
const int FRNT = 5;
const int REAR = A0;
const int FULL_LIGHTING = 6;
// misc
const int SRN = 7;
const int ALERT = 8;
const int CLR = 9;
// status bools
bool leftfldon = false;
bool frontfldon = false;
bool rightgldon = false;
bool frnton = false;
bool rearon = false;
bool fullon = false;
bool srnon = false;
bool alrton = false;
bool clron = false;
// read ints
int leftfld = 0;
int rightfld = 0;
int frontfld = 0;
int frnt = 0;
int rear = 0;
int full = 0;
int srn = 0;
int alert = 0;
int clr = 0;
// custom functions
bool checkButtonStatus(int thing, bool thing2) {
  if (thing == HIGH){
    thing2 = !thing2;
    Serial.println(thing2);
    delay(450);
}
}


void setup()
{
  pinMode(LEFT_FLOOD, INPUT);
  pinMode(FRONT_FLOOD, INPUT);
  pinMode(RIGHT_FLOOD, INPUT);
  pinMode(FRNT, INPUT);
  pinMode(REAR, INPUT);
  pinMode(FULL_LIGHTING, INPUT);
  pinMode(SRN, INPUT);
  pinMode(ALERT, INPUT);
  pinMode(CLR, INPUT);
  Serial.begin(9600);

}

void loop()
{
  delay(75);
  leftfld = digitalRead(LEFT_FLOOD);
  rightfld = digitalRead(RIGHT_FLOOD);
  frontfld = digitalRead(FRONT_FLOOD);
  frnt = digitalRead(FRNT);
  rear = digitalRead(REAR);
  full = digitalRead(FULL_LIGHTING);
  srn = digitalRead(SRN);
  alert = digitalRead(ALERT);
  clr = digitalRead(CLR);
  checkButtonStatus(leftfld, leftfldon);
}

Try

Worked great, thank you!