I didn't make it!
I'm one of those idiots who went through the main quest up until pripyat without finding Strelok's cache. Got through X16, got a message about Guide and Cordon appearing on my screen, but no Quest. Eventually got Strelok's Cache, but I can't find Guide. I've checked the spot he's supposed to be; only a dead Fox. I know the door thing can be forced open with a Gauss rifle, but I really wanted to actually play the game through. Any way exist to force him into existence or reset that specific quest? Existing mods? Console Commands? Learning Ukrainian and cursing out my computer?
Restarting the game and doing the quests in order seems to be the only solution I've ever seen.
Sometimes Guide gets killed. look around and see if you can find his body and click on it. It will fullfill the quest. If not, try previous save aournd x16? And yes, I have made the same mistake several times.
If you aren't playing vanilla (unmodded), some mods (aliVe and mods based on it, like STALKER Rebalanced and LURK) permit you to see Sidorovich about a dog, and pay some extortion fee for the info.
If you are playing vanilla, you can check your tasks, including the failed list (although it should not appear there). If you indeed saw a message in X16 about seeing Guide in Cordon, he should be there as [COLOR=Sienna]FEARLESS[/COLOR] noted. But if you didn't find Strelok's cache, you are not going to get the task to see Guide.
As [COLOR=Sienna]ShadeC4[/COLOR] mentions, you have to do the tasks in order, and that includes (spoiler)
If not, you can give yourself the continuation of the task in several ways.
The info_portion you get from Guide is esc_find_doctor_start. You can give that to yourself to get the next task (requiring that you see another man about another dog), although that will require modding your game anyway.
You can extend your reach (requires modding; edit gamedata\config\system.ltx, and increase take_dist under [inventory] temporarily to 10) or use grenades outside the Pripyat hotel room window to get the device you need to open the door. If you use grenades, I suggest saving/reloading until it knocks the device close enough to reach through the window.
If you are running pure vanilla patched to 1.0004 or later, you can get the Zone Reclamation Project (either ZRP 1.05 Test R10, or the MonoMartyr demo and update) to get around the problem in your current game. You do not need to start a new game.
In the ZRP 1.05 Test R10 version, you can give yourself the progress that adds the "Find Guide" stuff to your game. Install the ZRP, modify the fsgame.ltx file per the instructions, then start STALKER. The version info on the main menu's lower left should note that the ZRP is running.
Load your last save. When the game is running, press Esc to return to the main menu. Press T for the Teleport menu, click the "Just equip for level" checkbox (so that you don't teleport to Yantar or anywhere else), then select the "Yantar Lower Level" chapter (the first chapter after X16) and click the Go button.
Now Guide will spawn in Cordon and you can see him about a Doc. :lulz:
ZRP stuff -- click the Download link there.