Hi @episod,
In my App there is a tweet details page which has a favorite button. Suppose there was tweet with ID 1. This tweet was retweeted by some user and got ID 2. On my tweet details page, when I call favorites/create with ID 2, it actually favorites ID 1 (makes sense).
However if I go to the same tweet details page of ID 2, I want to show that it is already favorited. ID 2 is NOT available in favorite/list.
What I am currently doing (as a work around) is, get the ID of original tweet using retweeted_status.id_str. Then call statuses/show with this ID to get the favorited flag of original tweet.