Ridsdale was spotted in the directors' box at Home Park during their win over Huddersfield Town on 23 October.
Keith Todd, the Plymouth chief executive, explained it away as part of Ridsdale's holiday in the south-west.
But Todd's explanation seemed shaky when Ridsdale again pitched up in the directors' box when Plymouth went to Oldham on Saturday.
Now Todd is fighting a rearguard action. "Unbelievable, isn't it," he laughed with the Guardian, when asked about Ridsdale's latest appearance.
"He was not an invitee of ours. He was invited by Oldham and we happened to be there. I am not expecting it to happen at future matches."
And Ridsdale? "I'm a football person, I've been in the game 25 years," he said. "The base I left at Cardiff is proving I can do a decent job. I'd love to be back involved in football."