Wait until tomorrow and see if other people chime in... someone else may have an insight into what you should do. Nothing is going to happen to the bougie overnight.
Root rot will show itself mainly by wilting leaves... they look as if they are dry. People then tend to over water, and it just accelerates the process. By wilting, I mean that the leaves will droop and wither, like limp lettuce. This will happen to all of the leaves, so don't mix it up with the regular dropping off of older leaves, which of course all trees do.
Don't fuss too much over the tree, you don't want to make too many changes. There's plenty of time to consider, and get more advice.
It's hard to both give and receive advice over the internet, since we aren't physically able to see the tree and the conditions. Your best bet is to read, research, ask questions, and
apply what your common sense tells you.
Bayer can be purchased at most nurserys, you can call and ask before driving anywhere. They have multiple products, but we have been using the "All in One Rose and Flower Care". If that isn't available in your area, you can ask for the kind of systemic that is diluted in water and applied to the soil, that would be used on roses. Then follow the directions for the least amount, which I THINK is about three tablespoons per gallon, so maybe use two tablespoons in a gallon. (Check this, make sure that it's right) USE GLOVES and wash everything very carefully after you're done. Water the tree with the systemic, right down at the soil, NOT applying it to the foliage, until the medicine water flows freely out of the drainage holes. Then you can re-apply in about two weeks, another diluted solution. There are many other ways to deal with the problem, this is only one way, but it is the way that I have had some success with in my limited experience.
Joanie