What you're doing is perfectly fine and normal. If necessary, confidently walk through the steps you'll take to research the problem, especially if you have any idea of the soft resources (other people, internal docs) you'll need. Now you're communicating the process of task estimation to both the asker and any juniors in the room. This can really help managers to calibrate their own expectations of the work involved, which helps them to "spend your expertise" more wisely.