As you will know, the usual sequence is
- flight zero'd and removed from sale
- flight cancelled, email and SMS, perhaps a day or two later
- MMB updated
- App updated (usually a cache refresh needed to align with MMB).
Of late if you go into the App and down to Manage My Booking there, it's sometimes clearer when there is a cancellation

However almost every permutation of the above seems possible. I would leave it overnight, and then if you want to do something about it call tomorrow, but all things being equal it's best to leave it for as long as you can, to maximise your flexibility.