I honestly can't tell you if the strip was even on there when I moved in 12 years ago, or I'd have checked

Closer inspection seems like there IS a second track, but that it just bent over time from the door being slammed shut... maybe with a second set of hands it'll work. And if not, I'll do the single track method!

Looking at that Amazon one, it seems I can get a double track one, but shave a bit off each side to fit them into a single track like they do in the images on Amazon no?