I'd say if you witness some kind of wonderously miraculous event that surpasses anything you'd ever believed was earthly possible, but there's some guy standing right there pressing buttons on a machine, then it's a pretty good bet that what we're dealing with is still technology and probably not magic.

Unless you've got a telepathically-activated telekenesis machine, and are sufficiently advanced enough to hide it in the other room, so nobody can see what's making stuff happen. That might blur the distinction a bit. I anticipate that this kind of technology would be primarily used in magic shows.