***** NOT A TEACHER *****
I believe that you are 100% correct:
I cannot answer your question, but I am bumping it in case someone else can. = There is a good possibility that of all the great
teachers at this helpline, at least one may know the answer.
I cannot answer your question, but I am bumping it so that someone else can. = I have no doubt that someone else can and will.
Take your umbrella in case it rains. = Rain is NOT predicted, but the sky is dark, so one never knows. Don't take any chances!
Take your umbrella so that you will have it when it starts to rain. = The newspaper says that it will rain later today.
If you do NOT have too much confidence, you can add "just":
I am bumping your question just in case someone else can answer it. = I am the smartest question answerer here. If I cannot
answer your question, I doubt that anyone else can. But miracles do occasionally occur. There is always a very, very small possibility
that someone else can answer a question that I can't.
Student or Learner