To OP:
This is not a new feature; it has been there since the beginning. If your phone works like most, if wi-fi is not available for any reason, the phone switches to use cell data. If you are in a big store, even cell data may not even work, and that is why the no network message appeared.
This is not the app's fault. because you cannot get a wi-fi or cell radio signal if there is not one, or it is blocked by large structures like buildings, mountains and such. No internet access, then it's no go.