My son put his toothbrush in the toilet

Okay so this happened a couple weeks ago and Im still shook so I need to vent. On Dec. 29th my husband and I went out of town for 3 days for my birthday/New Years. We had a GREAT time and it was very well needed. My mother in law watched my kids the whole time we were gone and that was fine. A week after we got home my MIL told me about my 3 year old son brushing his teeth in the toilet water while she was tending to our 1.5 year old daughter. Like okay shit happens, I know that but if I would have known right when we picked them up, we would have stopped to get him a new toothbrush on our way home but she didn't tell me so for a whole week I brushed my sons teeth with a toilet toothbrush. My MIL told me Im overprotective for throwing his toothbrush away. 😂 I love her so much but god damn I'm still traumatized and my husband and SIL's all just thought it was hilarious.