I was going to do some sprint intervals today, but during the first interval, the chain immediately started to skip very badly. when i stopped to check, I found one of the links had completely ceased up. there appeared to be a metal shard stuck in there, causing it to be ceased up. I have no idea where the metal shard came from. I broke the chain and put it back together to get it out, and only got it to be partially unstuck, such that I was still able to finish my 30 mile ride that way. By the time I got home to diagnose it, the chain was completely fine, except for the fact that I can no longer locate the link with the broken seal in order to replace it with a quick link. (next time I use that chain, I'll carry a spare quick link)

so what do you think happened here?

do you think i can safely use the shimano chain with one of the links with a broken seal?