St. Augustine says that the Good Thief, if not already Baptized, could very well have been Baptized/Washed in that Blood and Water which flowed forth from the Lord Jesus Christ's Pierced Sacred Heart on the Cross. Whether that was the case or not, in a sense that is what happens in every baptism. As the water flows on us, the Blood is mystically applied to us, and our sins as washed away, as Acts 22:16 clearly shows.
St. Augustine: "For, to say nothing of the opinion that he might have been sprinkled with the water which gushed at the same time with the blood out of the Lord’s side,
2445 as he hung on the cross next to Him, and thus have been washed with a baptism of the most sacred kind, what if he had been baptized in prison, as in after times some under persecution were enabled privately to obtain? or what if he had been baptized previous to his imprisonment? If, indeed, he had been, the remission of his sins which he would have received in that case from God would not have protected him from the sentence of public law, so far as appertained to the death of the body. What if, being already baptized, he had committed the crime and incurred the punishment of robbery and lawlessness, but yet received, by virtue of repentance added to his baptism, forgiveness of the sins which, though baptized, he had committed? For beyond doubt his faith and piety appeared to the Lord clearly in his heart, as they do to us in his words. If, indeed, we were to conclude that all those who have quitted life without a record of their baptism died unbaptized, we should calumniate the very apostles themselves; for we are ignorant when they were, any of them, baptized, except the Apostle Paul.
2446 If, however, we could regard as an evidence that they were really baptized the circumstance of the Lord’s saying to St. Peter, “He that is washed needeth not save to wash his feet,”
2447 what are we to think of the others, of whom we do not read even so much as this,—Barnabas, Timothy, Titus, Silas, Philemon, the very evangelists Mark and Luke, and innumerable others, about whose baptism God forbid that we should entertain any doubt, although we read no record of it?"
https://www.ccel.org/ccel/schaff/npnf105.xvii.vi.xii.html