My dear, the damage would not occur so quickly. It would be a long term process.
The way your question is worded you give the impression this has happened other times.
Bile is most likely the cause. I’m guessing you drank some milk on an empty stomach. If your stomach is high in acidity it could cause a reaction with the milk. If you did have an empty stomach when you had the milk, try avoiding that in the future. Your best bet is dry toast before having the milk. Also, you might ask your doctor if you should be using an acid reducer.