This story seems to come from the book: The life of Saint Thomas Aquinas: biographical documents; by Kenelm Foster; Longmans, Green, 1959
In the book is a translation of St. Thomas’ First Canonization Enquiry the Archbishop of Naples held in 1319. It says a lot about different miracles. About this, it says:
*Asked about miracles - whether he knew of any worked through the merits of Thomas either before or after death - the witness said that when Thomas died his body was buried at first before the high altar, but then the monks, fearing it might be taken from them, transferred it secretly to St. Stephen’s Chapel in the same abbey-church. But about seven months later Thomas appeared in a dream to a brother James, who was prior at the time, and said:‘Take me back where I was at first.’ So they took him back, with due solemnity. (This dream was and still is commonly talked about in the monastery.) And when the tomb was opened a delicious fragrance came out, filling all the chapel and cloister: whereupon the community sang the Mass Os justi meditabitur sapientiam, etc., in honour of Thomas as of a saint; they thought the Mass Pro defunctis hardly suitable for such a man.
All this the witness knew because he was there and saw it for himself; it happened about seven months after Thomas’s death; but he could not be sure of the month or the day. Asked who were present, he said ‘the whole community’… Asked who had called him to the place where the fragrance was smelt, he said he himself smelled it; it drew him to where the tomb was.
Asked if he knew of other miracles attributed to brother Thomas, the witness said that he had heard of many; and in particular that when Thomas lay sick in the castle of Maenza and was urged to eat something, he answered, ‘I would eat fresh herrings, if I had some.’ Now it happened that a pedlar called just then with salted fish. He was asked to open his baskets, and one was found full of fresh herrings, though it had contained only salted fish. But when the herrings were brought to Thomas, he would not eat them.
The witness spoke too of a Master Reginald, a cripple, who was cured at the tomb of brother Thomas.
Asked how he knew of these two miracles, he replied that that about the fish he had from brother William of Tocco, prior of the Friar Preachers at Benevento, who himself had it from several people at Maenza, where the event occurred. The other story he had from brother Octavian (mentioned above) who averred that he had seen it happen. And in the monastery these miracles were common knowledge.
As mentioned, of the miracles reported here, the ones after St. Thomas’ death would have been of more importance.