Nostalgia.

lets invite pennywise inside here.

ok

Then I don't know what to tell you. Those are all Half-Life 2 textures. There never were textures from another source on this map. I'll see what I can do, but the outcome may be the same.

I have HL2 content from the game HL2

Okay, I see your problem. It looks like you're missing HL2 content, which doesn't make much sense. Open gmod and make sure that you have HL2 content on there by pressing the icon down on the bottom of the screen, it should have a controller on it. See if Half-Life 2 is checked off. If it isn't checked off, check it and restart gmod. If it is, then you'll need to delete your local gmod content and redownload the content. I'd do the same with Half-Life 2 as well (even though it may not make a difference, it may).

I can't paste the screen shots to my comments so you'll have to go to my profile

so I copied the screenshot after I press show on disk and I tried to paste it on my comments but it didn't work.

ok

Sure you can. Post the screenshots on Steam and make them public, then copy the urls and paste them into your comments

I got the screenshots for both elementary, and the SF2 sewer map but I can't post the screenshots to your bugs discussion.

I'll try

Show me in screenshots. Send them to the Bugs discussion.

Well, I don't know what to tell you. Everything has been HL2 textures in the past and are now.

this map has missing textures

WHAT THE *insert f word here* uhhh FOWA?! XD