I feel I handled this badly. It's too late to redo now, but I'm curious what you would have done.

A friends of DH's (and mine, but DH has known him nearly all his life) recently visited us one evening. We do not see this friend nearly often enough, and have been trying to see more of him. Our kids were in bed and we eventually suggested watching something from our DVD collection.
Friend picked an episode of a show we haven't seen in a while; DH found it and we started watching. A little bit in, I had a suspicion, wandered off for a moment and Googled the episode.
Sure enough, it was one that had a major plot thread (and a particular scene) in it that I find really disturbing. Call it a trigger, even.

It's been so long that none of us even (I'm pretty sure friend included ... he picked it for a different reason) remembered that particular plot thread.
I didn't return to the living room to conclude watching. It's not uncommon for me to come and go while friend is here (like I said, he's known DH far longer than I, although I consider us pretty good friends), but I just didn't return at all for the next hour.

I didn't know what to say. Afterward, friend made his goodbyes and left. I bid him farewell, but felt horribly awkward.
DH says to let it go, that friend probably figured it out on his own. (Like I said, they didn't remember this particular plot thread either.) I probably should have returned and explained why, but it's something I felt even more awkward bringing up in front of him.
What should I have done?