Dick and Lil Dickens, both in their 80s, mistook a warehouse where the party took place for a New Year's Day jumble sale, reports the Daily Mail.
The warehouse, in Cambridgeshire, was home to the end stages of the alleged illegal rave where approximately 1,000 people had spent their night.
Dick said: "We had been out shopping and we saw all these cars outside. We thought it was a sale.
"When we realised that it wasn't a sale we left. We're in our 80s so we don't want to get mixed up in anything like that."
It's estimated that £50,000 worth of damage was caused by the rave, including ripped-down ceilings and smashed doors.
North east Cambridgeshire MP Steve Barclay said: "This was serious criminality causing serious damage, with the culprits breaking into a business premises and using illegal drugs."