Two year old with lethargy

Patient: My two year old woke up very lethargic, i couldnt get her to stay awake and was very limp, she went 16 hrs without urinating, she had no fever. When i went to er the doc said there was nothing wrong and that her ears and lungs were fine. My question to you is was the doctor just being lazy because i felt that he should hae done more to find out why she was like that as she is very active normally?