The Dear Shelby Answer

I read different variations of this question in advice columns all the time, and invariably, I disagree with the answer. So today, I'm going to play advice columnist, and give a D/s version of what I think the appropriate response should be.
Keep in mind, given my own personal dynamic, the Husband here is the Dom, and the wife is the sub.

Dear Shelby,
I just found out my best friend has been putting the moves on my wife. While she has not gone out of her way to welcome these advances, she has not shot them down, either. What's worse, she never told me about them; she didn't want to ruin our relationships.
I found out about my so-called best friend's advances on my wife through looking through her cell phone texts. I know I was snooping; I know that was wrong of me. But now I don't know what to do. Should I confront my wife? Confront my (ex) friend?
Sincerely,
Confused Husband

(Typical advice columnist answer: You were totally wrong for snooping through your wife's texts, now you have to come clean and apologize, tell her you know about the texts, go to a therapist, blah blah blah)

My answer:
Dear Confused Husband,
First of all, you did nothing wrong by checking your wife's phone. That is YOUR RIGHT as her husband. In your house, you are the top of the chain of command, and as such, it is your job to make sure everything and everyone under you is running smoothly. Spot checks like this should be expected.
In other words, you do NOT owe your wife an apology for looking through her phone.
Second of all: your wife should have come to you as soon as the first advancement was made by your friend. Again, you are the top of the chain of command, and you cannot do your job unless you have all the information available.
However—and this may be hard to hear—if your wife was, for some reason, too afraid or hesitant to come to you with this, this is something for which you must take responsibility. You must find out why your wife's first, instinctive reaction was not to come to you. Did she fear you would lose control? Did she fear she would lose you? 
Are her fears justified?
Did she want to keep the possibility of a more intimate relationship possible with your friend?
The only way you're going to get answers to your questions is to talk to your wife. Make it clear you offer no apology for going through her phone, but do express regret for not making it clear, from the beginning, you expect her to come to you with these matters posthaste. Stay calm and in control of your emotions and the situation. Listen to what she has to say, but make it obvious in your demeanor and attitude that while you take her wants into consideration, whatever happens now will ultimately be up to you.
Make a contract between the two of you outlining what you expect of her in the future, with clear guidelines—and exemptions, if any. Perhaps you don't mind if your wife has some fun on the side with your friend...or perhaps you do. Either way, she should always feel safe to come to you with whatever is on her mind.
The last thing is to punish your wife soundly to assuage any guilt she may still be harboring for disappointing you.
The punishment will hurt in the short term, but in the long run, it will help both of you move on, and learn from this experience.