I agree. if mask didn't mark it, there is no way I would have been able to get it. I ended up watching the bot a bunch of times trying to figure out where the opening was. It wasn't until like 15+ tries after it being marked that I could finally see the small opening.
The problem is that either Valve removed a texture that this bonus utilized, or it was packed improperly when the fix version came out. I have uploaded surf_ardon_refix, and ported all map times/bots to the new version.