If you press enter/return after typing that into the box it'll load up the full search page and watch dogs shows up there - just not in the drop-down one for some reason..I've seen some similar cases in the past, though I've got no idea what causes it to happen.
Adding it to the 'games I'm playing' stack is working fine for me as well once you're onto the game page for the game. As such, I suspect it's just not appearing in that particular search method you used.
@robotopbuddy: ok, thanks! I only tried the quick search box method because I was updating the whole stack, so I wasn't in a mood to actually enter a game's page one by one (simply because all the others showed up fine)
@robotopbuddy: any way to edit the thread title then? to tell you the truth I didn't even know it was possible to add to stacks via a game page (I was looking for it after your response, then I found it under "+Follow"… took a while to figure that out…) that's why I didn't specify the search box in the title...
...oddly, my post didn't go through at all, so I guess I'll rewrite it:
Yeah, it's under either of the 2 +follow(ing) parts, would've mentioned that but it didn't really cross my mind that it wasn't clear where it was. Thankfully you found it anyway.
As for editing the title - I just did it, not sure why I didn't earlier tbh, I really should've. You can edit the title of your own threads via the "full edit" button next to the "edit" button on the 1st post of your threads though - alternatively you can also right click->open in new tab the "edit" button (or just add manually add /edit to the end of the thread URL of your thread), but it still has to be on the 1st post to edit the title anyway.