The Waiter Who Assumed I Didn’t Want My Leftovers

I was enjoying dinner with an old friend at a high-end spot last night—and by “enjoying” I mean “jawing incessantly”—so to be fair, I don’t know how our terrific waiter slipped in long enough to take our order.
I only finished half of my gnocchi, but had designs on taking the rest home for the next day. (I understand that some disapprove of requesting doggie bags in high-end places, thinking that it’s tacky and makes the diner look cheap. Me, I disapprove of waste and inflated portions, and think that caring so much what onlookers think is tacky and cheap. Maybe that’s just me.)
At some point while we were yammering—my gnocchi disappeared. Our waiter rightly assumed I was finished; I had set the plate slightly off to the side. Was he wrong to assume I didn’t want it?
In his defense, he would have had to interrupt a ridiculously lively conversation to ask. Many waiters are coached—rightly, I’d argue—that interruptions at table should only be a last resort. Is inquiring about the fate of a half-eaten plate of gnocchi a worthy intrusion?
Or is taking the plate away a waiter’s default position; a doggie-bag request the diner’s proactive responsibility?
I genuinely want your input. Actually what I really want is the rest of my gnocchi.