The prophets (inspired preachers) spoke to groups, for general attitudes and ideas, making them accountable to the gospel through Spirit inspired authority and conviction.
In most old commentaries and theology there are two aspects of prophecy 'predicting the future' or 'declaring the mind of God' generally. Both when referring to them as a gift, to be a special inspiration of the Holy Spirit. In the fist case obviously extraordinary and in the second, enhancing a persons natural abilities to declare the word of God with an unusual amount of conviction and accuracy.
With regards to the situation at Corinth we seems to have several people with the second gift of prophecy but this gift is very similar to what any good preacher would hopefully have each Sunday. One could say this gift still exists just not in the unusual proportion that it may have existed at that time. What is unusual or extraordinary is that there were so many good preachers ready to share their word burning upon their hearts that they had to take turn speaking and let the others judge to make sure what they said was really scriptural or not. The others could not judge if the word was just calling out an individual but must be judged for the general truthfulness of the message.
Hearing the word by an inspired preacher will definitely disclose the secrets of our hearts because this is what God's word does whenever we read it. The power of God's word to do that however is greatly enhanced under the power of the authority of the Spirit.
A Cessationists would think it rather devilish to imagine that people merely guessing under their own inspiration or even the Devil's, what the 'secret sins' of another might be, for example revealing that so and so drinks whiskey all the time, is not what this verse describes. The declaration of prophecy is always a gospel oriented positive message, that includes our total depravity and the great salvation from it, that is what discloses the secrets of our hearts.
True, in rare occurrences, even secret sins are made manifest for gospel purposes. Jesus did mention the 'five husbands' to the woman at the well (John 4:17) but this was not to publicly insult her like an accusing devil but in the silence of their conversation to encourage her faith in his loving condescension towards her.
The secrets of our hearts are not merely 'secret sins', but our hearts in general that we do not understand until touched by the gospel under the anointed preaching of God's word.
12 For the word of God is alive and active. Sharper than any
double-edged sword, it penetrates even to dividing soul and spirit,
joints and marrow; it judges the thoughts and attitudes of the heart.
13 Nothing in all creation is hidden from God’s sight. Everything is
uncovered and laid bare before the eyes of him to whom we must give
The New International Version. (2011). (Heb 4:12–13). Grand Rapids,
On a personal note I do think that this gift of inspired preaching does rest among many lay people in the world, that might not be considered preachers. It often shows up in bible studies because most churches would not permit the gift to operate during a Sunday morning sermon. See - Origins of Monologue Sermons