Episode #2.5 - S2-E5
Stupidity: For the plot to go the way it is shown, the police, that were specifically looking for poison from an unknown source, had to completely neglectful checking the trash bin (or they'd find a bottle with - literally - the name of the victim in big glitter letters, which is sure to draw attention!) and somehow miss the fact that the victim's food and drink were into a mess of shattered glass that made at best dubious which one her real glass was. Both are pretty huge oversights nobody seems to care about and that would have raised at least some suspicion from even the most casual investigator, especially when no poison was found in the glass.
Answer: There's probably no particular reason. Sets and props on long-running TV shows often change as needed and for various reasons throughout a series run.
raywest ★