Originally, they would seize collateral from the finder until he brought its nesachim. [But] when they began abandoning it and fleeing, beis din instituted that its nesachim should come from the public [treasury].

Said R’ Shimon: Beis din instituted seven ordinances, and this is one of them. [The others are:]  [If] a Gentile sent his burnt-offering from a faraway country and sent nesachim with it, they are offered from his own; if not, they are offered from the public [treasury].  Similarly, a proselyte who died and left offerings, if he had nesachim, they are offered from his own; if not, they are offered from the public [treasury].  It is a stipulation of beis din regarding a Kohen Gadol who died that his flour-offering be brought from the public [treasury].  R’ Yehudah says: [It was purchased] with his heir’s [money].  [In this case] it was offered whole.