It is possible to come under the influence of the Holy Spirit without being converted.
I have often seen this with the children of missionaries or preachers. The children are raised in an environment that is more than just the Christian culture. Particularly when parents are really sold out, there has to be a presence of the Lord in the home that is real, and genuinely impacts the children. Often, they are touched and respond to altar calls or other invitations. Yet when the years pass, it seems that they have shed the Christian skin and have rejected the truths of their childhood.
Only the Lord knows what is going on. There certainly are cases where the person is a prodigal. When that is the case, he or she will readily say that the experience with the Lord was real, but there was a stepping away from Him. Other times, there are people who seem to be moved, seem to want the Lord, but just never taste Lordship because they have never really met Him.
I am one who believes that if there is no Lordship, there is no Lord. On the other hand, it is not up to us to read the heart. The Lord does not do everything in the same order with all of His children.
What are we to do? Pray and love. Ask for wisdom. Then pray and love more.