At first reading I was sceptical about JC's theory, but it sounded more plausible when I thought about it.
Mardee, modern cannabis gummies look for all the world like regular gummies you'd find in a candy store.
I've never tried them.
Edible cannabis can be a real experience in high doses, and very easy to get there from a pack of modern commercial gummies, like you'd find in LA.
As a travel tip, I'd always recommend inexperienced visitors to Amsterdam steer clear of coffeeshop brownies. It's a real gamble the way it's regulated (i.e. none). It's easy to get a dose that will have you moonwalking like MJ for a day or so. Or get nothing. You can't buy commercial, packaged gummies in Amsterdam as far as I know, but I believe city bylaws allow it in other Dutch cities. They're actually much safer as the dosage in mg is on the bag.
Edible cannabis could be really scary for the inexperienced user at high doses. It's really cruel putting someone through this if they're not expecting it, even if doesn't really cause physical danger, to the sound of mind and body anyway. JC could be on to something though.
Surely they'd know the perp from the seat number and passenger list?