Is this considered hiding it from your partner?

So basically the question is if your partner had a friend that while you were gone out of state for a week they confessed feelings for each other and he/she planned on leaving you for said friend. But then you found out and they decided to stay with you. Agreed to stop talking to said person and block them on everything. Now a years gone by exactly a year actually and your partner is now talking to this person again. But never told you that they were or asked how you felt about it and also wouldnt let you even go on there phone to look at a app to find a balance for a card you share that only they have the app for. Also the only way they found out was from going through there phone while they were asleep because you knew something was off. Would that be considered hiding that your talking to this person again from your partner?