"Without his initiative, who knows when or if Caylee would have ever been found?" said Mark NeJame, who formerly represented the child's grandparents.
Investigators found Caylee's remains earlier this month after Roy Kronk tipped them to a bag he had seen in a wooded area in Orange County.
Caylee's mother, Casey, 22, has been charged with murder, child abuse, aggravated manslaughter and lying to investigators about the child's disappearance.
NeJame, while working on the case, received the $5,000 to help find Caylee, The Orlando (Fla.) Sentinel reported Tuesday. NeJame has not named the donor or donors of the money.