The way I approach this is the following:
1) Assume that there is some natural or normal way the Pentecostal preacher knew about you. Perhaps your friend told a friend and it got back to the preacher. The preacher then uses this as a way to "prove" she has spiritual gifts. It may even be subconscious after years of seeking after this.
2) Assume it is a demonic deception.
3) I believe that God can work through non-Orthodox, but the key to discernment is what is the fruit? If the fruit is to get you out of the Church of Christ, then obviously this is not from God. Something that might be "from God" would be if an Evangelical pastor goes to a witch doctor in some tribe and converts him to Christianity. Sure, it's not to the Church of Christ, but it's a step in the right direction using the available means. I could see God using that as a step. Ultimately, though, we really can't speak with definitive judgment on what happens outside the Orthodox faith.
As I wrote in an article on a parish website:
This leads us to the question of measuring such experiences. Is there a way one can know which of the above options any given experience was? Is it even profitable to do so? The Orthodox response might be that it is difficult to know, and is probably not profitable to investigate. A big clue though would be the outcome; as a result of any given experience, did the person come closer to God and His Church, or slip further away? Jonathan Edwards, the famous New England preacher, had ecstatic experiences which led him to become a Calvinist. Many Mormons cite a “burning in the bosom” as proof of the Book of Mormon.
For Orthodox, however, religious experiences before conversion were often steps on the path that ultimately lead them to fulfillment—and what they experienced in Orthodoxy goes far beyond the experiences of the past. Orthodoxy builds on and completes prior experiences which while good were steps, not the end in themselves. By seeing where the person ended up—in or outside the Church—and if they died outside the Church by judging whether they came closer to it in their life (for instance from paganism to Evangelicalism) are good indicators, but again are highly subjective. It is best to leave such uncertainties to God, who is a just and merciful judge.
