Barry Dunn lost the piece when he flew from Mackay in Queensland to Sydney Thursday. Officials at the Mackay airport found it at the X-ray security screening section, the Australian Broadcasting Corp. reported.
Dunn said he found the nugget at the goldfields using a metal detector and wanted to show it to friends in Sydney.
"I can put up with losing things but I can't put up with the wife nagging me how stupid I was but nevermind, I was stupid," Dunn said.
"Normally I wouldn't carry nuggets in my pocket but it just went in my pocket like a box of matches and I didn't think much about it."
"(It's my) 66th birthday today and that's the best birthday present I could ever get," Dunn said after hearing the piece had been found.