The changes made in Twitter's 1.1 API resulted in the need tto remove the traditional "Interactions" feature from TweetCaster. While we currently do not have an ETA on when this feature might be added back into TweetCaster, we’re working on alternative solutions for a future release.
A big question you may now have is, “Since the interactions tab is gone, how do I find out who followed me, retweeted me, favorited me, etc?” While perhaps slightly less convenient, most of what Interactions showed is still available in TweetCaster.
Who followed you: Your followers list is displayed in the order you were followed by people, so go to your profile and tap on Followers to see the newest follows.
Who retweeted you: Go to the retweets section and select "Of Me" at the top of the screen. This shows a list of your tweets that have been retweeted. You can select each one and select Who retweeted this.
Who listed you: Go to Lists (on Android phones, go to your profile then go to the lists tab) and select Lists Following Me.
Mentions: Show up in the Mentions area as normal.
Who favorited your tweets: Currently this is not available in the app.