JOEL - There are situations where one can receive revelation for others. The President of the Church receives revelation for all members of the Church in regards to matters of doctrine; A Bishop can receive revelation for the members of his congregation to help them with their problems; parents can receive revealtion and inspiration to help raise and teach their children. But these are situations in which a person has been given leadership authority over a specific group of people and therefore has the right to receive revelation for them.

President Wilford Woodruff said:
"Every man or woman that has ever entered into the Church of God and been baptized for the remission of sins, has a right to revelation, a right to the Spirit of God, to assist them in their labors, in their administrations to their children, in counseling their children and those over whom they are called upon to preside." (Wilford Woodruff, Millennial Star 51:548, June 2, 1889)

President Harold B. Lees said:
"As stake presidents, or whatever call is yours, you have a right to receive, and you are expected to so prepare yourselves to receive [and] be spiritually directed [by], inspiration. When we talk about prophecy, prophecy in the Church and the kingdom of God is not confined to one man. This is a nation of prophets. Every person who has the Holy Ghost has a right to prophecy, the gift of prophecy, within the sphere which is designated and outlined by the imposition of hands for each calling for which the individual is called." (Teachings of Harold B. Lee p. 419)

I think your mission president was generally correct in saying that one person cannot receive revelation for another unrelated person over whom they have no authority. We can always be inspired to do things for someone else or be inspired to help a friend with a problem; but it is unlikely that we would receive revelation about something specific that another unrelated person should do; especially for any life-changing decisions. That person should ask God for themselves, and receive their own revelation on the matter.