I did the quest and got the Ebony blade. After that I put it on a weapon plaque in Breezehome, the one that is just over the entrance door. A few game days later, it's disappeared!!! I tend to think that it's not normal.

The only things I did to my game recently is installing the high resolution packages and a few mods: Open cities Skyrim, Shadow fixing fix and Skyforge complete. I add that the weapon is not invisible; the weapon plaque is empty and it didn't get back to the room where it was in Dragonsreach either.

The Ebony Blade always falls off racks and displays, I ended up shoving it in a cupboard after having it fall off every rack and plaque in my Markarth home.
Yours may have glitched through the floor and is now gone forever.

This happened to me after Griselda put it on a plaque in her Riften home. Had to give myself another Ebony Blade with the console. Fortunately didn't seem to affect the count for number of people she'd fed to it.

Oh well, I'm not using it anyway.

Thank you for allowing me some of your time.

P.S.: I'll try something though and see what happens (player.moveto ...).

Yeah, don't put the ebony blade on a weapons rack. Same goes for the skull of corruption

Yeah, don't put the ebony blade on a weapons rack. Same goes for the skull of corruption