I came across this topic today after making the mistake of pushing the pin all the way through. Hey, it was my first attempt at changing the chain on my bike.
It had a ton of crazy suggestions like using a Dremel tool, or a hammer, or bashing it back in. After wrapping my head around the problem, I came up with a solution.
Here's a link to a tutorial I made on how to get the pin back in, even if you accidentally pushed it all the way through.
I'm sure the more experienced riders on here would argue that this weakens the link, et cetera. So I'm ready for that criticism.
P.S. This was my first attempt at this problem AND using iWeb (which I don't like at all!) I think I'll stick to Dreamweaver.
P.P.S. If this has already been covered, my apologies for wasting your time. I just couldn't find anything that could help me today and needed to come up with something on my own.