I will post what I find out, when I do. Fred, can you give me a picture of this out-rigging tube? Joel, the only steel is the bolt/pin. The wheel and the sleeve are both plastic. Good catch.
Also, Becky comes in to the driveway ahead of me when we get home, as we unhook a couple of miles from home due to some nasty turns in our road home. She told me that this part was laying on the pad when she arrived home with the toad, meaning it fell off before we left in mid-August. So, that means it could have come from any slide, but its still likely its the one I mentioned, due to its location when I found it.