My Sister Is A RN And She Coded And Had

My sister is a RN and she coded and had CPR done on me Friday night. She was taken to a hospital where she works at and was told it was a Methadone Overdose. She has never taken Methadone a day in my life. She takes soma, Ultram, cymbalta and Naproxen. What could cause this? They only did a urine test.