LBM, gently, I am concerned that this isn't your husband's first rodeo.
It's just a speculation on my part.
I suspect this is merely the first AP he's chosen that was so close/so visible to you. Right under your nose, as it were. He seems/seemed way too comfortable with that.
Experienced players tend toward playing, if that's all they want (and that's all most want) with other experienced players, or at least with people who are unlikely to burn down the house. Many will deliberately seek out married AP partners, wagering that the married AP partner has as much to lose as they do, and are thus less likely to blow up their lives.
I speculate that, if your WH is indeed a player, part of his wager with this AP was that she, like he, is the higher wage earner in the household. She has as much to lose, financially, in a divorce as he does.
She wasn't particularly on his radar until she became more physically fit, lost some weight, and then she became a viable candidate. The fact that they were both the higher income spouses should have made her a safer bet, but it didn't work out that way.
She fell into some sort of emotional bond and started imagining a future together, which he then had to manage.
The OW didn't drop the affair like a hot potato upon discovery, and go immediately into all out damage control mode at home with her husband, to protect both her income and assets and his. She went to see an attorney instead. That probably terrified your husband, who had no intention of disrupting his life or his finances with a divorce as the result of what he considered to be a casual dalliance.
He could have called her from your home, with his cell phone, right in front of you, to say his goodbyes. The goodbyes didn't need to be especially loving but they didn't need to be especially cruel, either. In fact, he *should* have done this right in front of you.
If he couldn't bring himself to do that, then he could have called from work. He could have used a friend's phone and called in the presence of a trusted friend who is supportive of your marriage. There are so many things he could have done short of buying a burner.
The fact that he kept the Tracfone card is suspicious to me. If it was truly a one and done, the Tracfone minutes card should have tossed with the burner phone- if the burner was tossed.
Check on this, but it's my understanding that one must buy "airtime" (access) and then buy minutes as well. Some minutes cards come with built in airtime. Some cards are airtime, with an allotment of minutes, which are refillable. If you still have that card, you need to take a good look at it to see what exactly it does for that burner phone. There is information there about the intent for that burner.
Maybe I'm naive (scratch, I *am* naive) but buying a burner phone immediately following DDay is not a rookie move in my book. It's a strategic maneuver by someone who was either thinking ahead, or has been here before.
I would think that a husband who was busted in his very first and only dalliance and was in crisis mode with his wife, trying to reconcile, saying he wanted to save the marriage, would avoid doing something as obviously incriminating as buying a burner phone like he would avoid the plague.
I'd bet, and this is just my gut talking, I could be very, very wrong- that this strategic maneuvering isn't so much about continuing the affair (although it could be, what do I know?) as it is about damage control.
If it's about damage control, that would bother me as much if not more than if it was about a continued connection between these two individuals.
The continued connection, while inappropriate and undesirable in terms of the marriage, is not surprising- these people had an affair.
If it's damage control, to me it speaks more to a player situation- someone who "knows the ropes" and is trying to get a situation back under control.
If this is the case, probably no one was more surprised than your husband when the AP "fell in love."
I'm not a huge fan of polygraphs. I've always said that if I felt like I needed to make my husband take a polygraph over any other woman (or anything, really) I'd save both of us the trouble, time and expense and go straight to the attorney's office. I'd sooner sleep with a snake than sleep next to a man I'd forced to take a polygraph.
In this case, however, if you choose to stay in this marriage, you will need a level set. The most important question I'd want answered out of that polygraph- and perhaps the only answer I'd really need- is how many other affairs/APs have there been. The answer to this question (if polygraphs work that way, I have no idea) will tell you what type of situation you are facing here.
A burner phone speaks to a level of sophistication and willingness to take risks that would need to be addressed, explored and explained to my satisfaction before I spent another night under the same roof with that man.