Who saw heaven and returned to earth?

I think the questioner is referring to 2 Corinthians 12:1-5:

I must go on boasting. Though there is nothing to be gained by it, I will go on to visions and revelations of the Lord. 2 I know a man in Christ who fourteen years ago was caught up to the third heaven-whether in the body or out of the body I do not know, God knows. 3 And I know that this man was caught up into paradise-whether in the body or out of the body I do not know, God knows- 4 and he heard things that cannot be told, which man may not utter. 5 On behalf of this man I will boast, but on my own behalf I will not boast, except of my weaknesses.

Although Paul appears to write in the third person, he actually explains that he is talking about himself. This is evident by him saying “I must go on boasting”, and then in v6-7 he says that he will refrain from saying more “so no one will think more of me than is warranted by what I do or say, or because of these surpassingly great revelations.” (TNIV)

The odd literary device of speaking of his own revelations in the third person appears to be because he is embarrassed by having to “boast” about such things in order to support his apostolic
credentials which some at Corinth were questioning.

Three Heavens in the Old Testament

The reference to the “third heaven” is interesting. Jewish cosmology seems to have consisted of three heavens: 1. where the birds fly (the sky); 2. where the stars are (outer space); and 3. where God dwells. Paul is clearly saying that he was “caught up” to God’s dwelling place. (Later Jewish writings refer to seven heavens.) In some places, the third heaven is referred to as the “highest heaven” or “heaven of heavens” — e.g., Deut. 10:14; 1 Kings 8:27; Psalms 148:4.

Third Heaven in the pseudepigrapha ‘Life of Adam and Eve’

See also the answer What is the Third Heaven? for information about some of the non-biblical Jewish myths which appear to have been causing problems in Corinth.