I don’t think so - my understanding is that the balance is your account’s balance minus any authorised transactions. Since the authorisation’s been reversed, it’s no longer deducted from your balance as the merchant may never collect the payment, in which case the purchase was free 
But the potentially pending payment makes me uncomfortable too & this looks like another good use case for a solution like this (although in retrospect, the solution I’m requesting is a bit ‘power usery’) -
Either way, I’m optimistic that Monzo will do something to help manage these unauthorised pending payments when the current accounts launch because it’s going to be even more important for users to know their ‘final’ balance in order to manage the overdrafts.