That can be confusing. I think the only notification comes before you click to go to a new area/Chapter 2 areas. You off cource know, that there are two ways to go the "main chapter 2 area", trought the mountains area, were the quest says the Lae´zels catche is and trought the Underdark, the Adamantine Forge I think it is called. The other way will be locked, when you make that decision. (But you can still return in Chapter 2 to the older areas, but after the ending of chapter 2/later events in chapter 2, you can not anymore.) Still be careful about leaving Act 1 area, I think some events will resolve themself if you leave. So yes it is very possible that you already slipped to Act 2.