I guess you're right, I kinda went too far. But when you think about it, those are the only two options as to why the same piece of graffiti is in both games.
What 'bout zis?
(half-life 2)
(left 4 dead)
Maybe I'm just a nitpicker, but these are obviously the same pieces of graffiti. Either the two games will be connected, or they're just using the same textures.
...
Yeah, luckily on the Nectarium levels, you can just leave him in a corner in the room where the vortigaunts are with Alyx, and pick him back up when you leave.
The only one I actually knew about was the one where's he's near the hotrod on the bridge, although I've tried several times to find him there and failed.
Ditto what Redfox said, plus, you need to remember that the infected respawn, and the survivors don't. The idea is to continually pick away at them throughout the map.
1st link is a 404 and the second one doesn't allow linking.
EDIT: Oh wait, it appears that after you click on the second one, you can just hit enter in the address bar and that works since it's not a link. Apparently I'm a l33t int3rn3ts f00l.