Using throwaway acct for this as it's sensitive.
My boss's wife has become convinced something is going on between us because we attended a black tie awards ceremony together (as in we went together in a taxi and sat at the same table, absolutely nothing else!) and she clearly checked his phone and found 2 photos of us at the event. He sent them to me afterwards so I could send them to my team, as it was hosted by a minor celebrity who was in the photos with us. We have never even exchanged WhatsApps outside work before. Literally a few messages saying he booked the taxi for x time, see you in the lobby, and a couple joking afterwards about some of the very drunk people on our table.
I got a message from her the day after asking who I am and what was I doing in a photo with her husband. I didn't reply initially because I was taken aback. I've since had a couple more, with a more insistent tone. Boss has been off on leave since the event.
I have no idea what to say, since it seems manager hasn't told his wife he was there with a female colleague. No idea if there's a history of cheating, we don't discuss personal lives in depth. We know each other's spouses' names, kids names, ask politely about the family etc but other than basic details I know little about his family life. I have heard rumours he used to be a party animal on work nights out, but sounds like that's years ago and when he was more junior, and I've never seen it. I've never even known him drink at a work do. I'm a senior manager, I'm married, and I pride myself on my professionalism. I certainly don't want any rumours starting.
If you were a worried DW, would you want the woman you suspected to message back and say there's nothing going on? Or would a denial not help really? Do I just stay out of it, let my boss know when he gets back and let him deal with his own affairs?