Why did DeWitt return the trophy to Eve's home, when she told him to take it with him to the party?

I'm very confused, because near the end of the movieIn All About Eve, Eve tells Addison that she does not want to attend the party, and asks Addison to take the trophy in her place instead. Addison agrees to drop her off at her home before he goes to the party by himself.

However, in the final scene, Addison returns to Eve's home to give back the trophy that she apparently left in the taxi. He hands it to Phoebe, who is told by Eve to put it on her suitcase.

It seems that neither Eve nor Addison have remembered that Addison was supposed to bring the trophy with him to the party.

Can anyone help me understand this? I've been looking on the internet for an answer but I have had no success. Have I misunderstood something here?