Nope it should always show a short preview after the shot. Try to reinstall the app on your device. Im shooting on an ipad air 2 fyi. Also go into setting and set photo playback to 2 seconds
Here is one that i'm pretty amped on since tonight i was able to capture some lightning on a 1 second exposure during a storm!
And here is a night time long exposure tutorial i made to help you out since i see a lot of questions about it.