(Spoilers Main) Randyll Tarly Must Be Either Blind Or Stupid

In season six, episode six of Game of Thrones, Samwell Tarly stole Heartsbane, the Valyrian steel sword of his house, right out from under his father's nose. And apparently the old man STILL hasn't noticed.

This season we have seen Randyll Tarly attending Queen Cersei at court and, later, riding into battle with Jaime Lannister. Wouldn't you want to have your fancy-schmancy magic sword with you for those kinds of things? I mean, I get that it's usually mounted on a wall, and maybe you don't take it down or look at it closely every day, but come on. I could even accept that you wouldn't bring it to King's Landing to see an unstable queen who might be planning to chop your head off, but in that case why would you bring your son and heir (the hilariously named Dickon) with you? And it still doesn't explain why you would ride into battle without it.

Even if he didn't notice right away, once he realized the sword was missing Tarly must surely have suspected Sam. And while he could not go to Oldtown in person to retrieve it, what with Jaime Lannister waiting, he could still send someone. At the very least you'd think he would be pissed and complaining loudly about his good-for-nothing, fat bookworm of a son. Randyll Tarly has never been shown to be the kind of guy who suffers in silence.

Did the producers miss something here? Or did Sam really get all the brains in the Tarly family?