Waiving Rights to a Lottery Win

In one of the synagogues in Bnei Brak, a lottery was held by the Association of Yeshiva Students for free entry to swimming pool for those who study for two consecutive hours within the framework of the association. The young man who won stated that he would not be in town at the time when the pool is open and therefore they should draw again. After a short while, the management of the pool called and announced that due to a technical problem, the pool would be closed today and they should come tomorrow. Now the association's management wonders whether they should give the entrance ticket to the swimming pool back to the first young man who won, as he will be able to go to the pool tomorrow.

Shalom!
The first boy’s relinquishment was effective, and the second boy has the right to the free ticket. The relinquishment was not made in error, since at the time of the relinquishment, the young man indeed could not go to the pool. Only after the relinquishment took place did the situation change.

Shulchan Aruch, Section Choshen Mishpat, Chapter 241, Subsection 2