Could be another queen in the hive, either non laying but probably virgin. Could there be an open queen cell on the edge of the comb or in some other hard to see location? Sounds like another queen is in there somewhere.
I have heard the exact opposite, can't remember the thread but it was said that they will instantly know she's dead. Granted I've only pinched one queen but they had cups started inEver heard of someone placing a dead queen in a trap? Why? Because her pheromones remain with her corpse for a considerable time. Leaving her corpse in the hive may be what is keeping the bees from building a queen. They do not know she is gone yet. next time you pinch a queen off take her away. the bees will realize they are queenless in hours, and happily build a replacement.