I called someone who is a higher rank than I do. Technically, he does have the authority to tell me what to do. While he is not my direct supervisor, he is a corollary supervisor to me in a way. I asked him what I thought was a pretty straight forward question. He didn't know the answer immediately, which is absolutely OK, but instead of saying, "Let me find out" and hanging up, he hemmed and hawed for 12 minutes (yes, I timed it, simply because I know he has this habit), all the while keeping me on the phone, only to eventually say, "I'll have to look. I'll call you back." During those 12 minutes, I would try to ask him a question pertaining to the original question (along the lines of, "Well, would this work instead?") only to have him start talking to someone else presumably in the office with him. I'd have to wait for that conversation to be over for him to answer me or at least acknowledge that I said something. At one point, I held the phone away from my ear and shook it just because I was so frustrated and could do nothing about it.
One of the first times I called him for something, I tried to ask him to call me back when he had the answer. Instead of agreeing, he just said, "No, it will just take a second." I didn't feel like I could argue with my superior. I also don't feel like I can insist he call me back when he finds the answer.
How can I politely tell him that the best solution is to call me back when he has the answer so that he doesn't waste my time when I could be doing something more productive (like maybe also trying to find the answer via different means)? I spent 12 minutes on the phone doing nothing when he could have just told me from the get go that he would call me back with the answer.