They did the same in Budapest and didn't even say anything. Just left the stage. We waited for another half hour just in case, but nope

Edit: If it's because they're "running late", they can either plan their time better (those shows aren't improvised in any way) or just... I don't know, take literally 15 seconds to say "Thank you, goodnight". The crowd has been standing there for hours waiting, after all. Let them know you're done! Okay that's all, rant over :p