I think I've gone and done it now...
We have a very old pool (built in the 50's) that had no skimmers. I recently had a local pool store add a skimmer to one of the supply lines. It most definitely looks rigged but allows for adding DE, etc. via the skimmer and allows for vacuuming with a skimmer basket.
This morning I managed to allow a skimmer sock to be pulled into the supply line. It appears to have totally clogged that line as there's no movement of water in that skimmer now. I pulled the skimmer (it's retro-fitted to a cast iron pipe with removable fitting) and still no suction on the cast iron.
I tried pushing a fish stick and fish tape (electrician tools for running wire) into the line in hopes of snagging the skimmer sock but there appears to be an elbow within feet of the port so I got nothing.
I'm fearing the worst now - that I'm looking at excavating the cast iron. Any other suggestions? Wondering if I can get some water pressure going the other way to push the sock back out?