I don't think it's so strange.
MH has people drink the orange juice diluted in water for the fast.
I asked my dentist about people who eat lemons and he said it is bad for the enamel, but as long as mixed with some water in a drink it should be fine. I love to drink lemon juice mixed with water, about 1 part fresh lemon juice to 2 parts water. Then I swish one mouthful of plain water when I'm done. Just to be on the safe side.
So if your orange was very acidic, I suppose it could have done some damage on a place that had already very thin enamel.