Toddler cut off circulation

My 1 year old found a yellow hair rubber band and put it on her wrist and im not sure how long it was on there or how i didnt freaking notice but when i did her hand was very very swollen, not a different skin color which was odd but very swollen and rock hard like something was in it. Were goin to the dr today because i will have the car i just wanted to know has this happened to anyone else ? And wat was the outcome if it did . Im just worried because this happened last night around bedtime and her hand is still swollen but she can still move her fingers