If a problem cannot be recreated in all manner of things in this life it will be deemed undiagnosable, not unreasonably so.
Since this is a cold start problem did you leave the vehicle overnight with the dealer? If not I would recommend doing so while also furnishing your video to show how you recreate it. If you've covered these bases already then I would leave the vehicle overnight at the dealer and then have a tech get in the cold vehicle with you while you recreate the problem. That would have been my approach after the first try.