No location/quest marker for griffin steel sword upgrade?

[Wobb the Great and Terrible!!!!!]

I have the quest objective in my log, but when I select it there is no location shown.

It's the griffin school gear upgrade diagrams - part 3 quest. I found everything else for this quest, but with no idea where to start looking, how am I supposed to know?

[Wobb the Great and Terrible!!!!!]

I'm not sure which it is without going through which I already have, but it's not pointing to another area, I'm in Skellige already.

But thanks for the info, next time I play I'll check both of those places you mentioned anyway just to be sure

[Tyralyon]

In case anyone finds this post later and is in the same situation (I was), the description BuzzardBee posted was a bit inaccurate... It's not actually in Urialla Harbor, but rather the houses north-west of it. I took a screenshot: http://imgur.com/a/dzjap
After finding the shrine, and using witcher senses to check the red markings on it, the quest updated and I found the sword.

[ⒺⒹⒸⒶⓈⒺ]

For me reloading a recent save brought up the quest marker, and it is exactly where TyraLyon stated.

[NKSedya]

the chest with the steel sword upgrade diagram is not interactable for me.
Re-loading the save fixed it.

[Crespoter]

Reloading the save game fixed it for me

[Red]

Same, reloading the last save fixed the issue for me

[Aksuuu]

reappeared for me after restarting the game