wild goose chases

Found the quote -- it's from what is apparently a classic book on Mathematical Problem Solving by Alan Schoenfeld.

The Wild Goose Chase in Problem Solving

When solving standard mathematics problems, students normally recall and apply learned procedures in a straightforward way. However, if the problem is unfamiliar, some students simply pick a method and keep persistently on the same track for a long time without getting anywhere. Schoenfeld (1987) described this behaviour as chasing the wild mathematical goose.

That's not the meaning I remember.

I probably got it wrong.

knock on wood
true confession
wild goose chase