Just to be clear, you deleted the video from your iPhone, but it’s still on your iPad where LF is installed correct?
If that’s true, then I’m not sure what the problem could be. If you deleted it from your iPad after you imported it LF then that’s kind of expected. LF doesn’t import the file, it simply references it from your camera roll. If you delete it from your camera roll, it’s gone from LF.
Oh, yes. I deleted it from the iPhone AFTER importing it to the iPad, and then into LF. It was NEVER on the camera roll; that was the reason for this whole workflow - I wanted to avoid uploading unedited video to iCloud because of slow transfer rates. I edited it in LF without problems. THEN I deleted it from the phone, and AirDropped the video to a Mac. Indeed, it's still running fine in LF on the iPad. Strange. I also made a copy of the edited file and exported it to the Rendered Movies folder on LF on the iPad. It's black there, too, so I know the problem was not in the data transfer to the Mac.