welcome to the club (although I suspect you're already there, with your line of work).
This is how I have to deal every day with various client reps, with contractors, vendors and with my own bosses. One would think that at least the professionals would know what information i would need in order to answer their request...but no. I have to be a detective-slash-diplomat to extract the data from them - and then they get irritated by "so many questions!".