With card transactions, first there is an authorization, then there is a settlement. If things go wrong during transaction processing, the merchant may not send a settlement and instead send a authorization cancellation
Typically in such cases we get a notification between few hours to up to 7 days that the transaction is cancelled. Once we get notified, the funds are applied back to your account.
If this has not happened contact us via the Settings section of the MuchBetter app.