Police were alerted and a man was arrested in Hagley Park a short time later.
"Big-ups to the police, I got my gear back and my instruments back in time for the parade.''
Lance Corporal Hickman said he was disappointed that someone would stoop to such a level on a special day.
"There were veterans arriving and it's a special day for them and a special day for all New Zealanders, so to think that someone would stoop to that, it's a bit sad.''
Inspector Mike Coulter said the man arrested was alleged to have snatched the bag as the band were setting up about 5.20am.
A dog handler, who was waiting at Hagley Park, saw the man and was able to arrest him.
"A 35-year-old man Christchurch man has been arrested for theft.''
The man obviously hadn't "computed'' how many law enforcement officers would be in the area, Mr Coulter said.