When I was traveling through Texas it came time for a new chain.They put on a premium gold X-ring chain because it was the only one they had, and it used a master link with clip, not riveted. Before I rode the bike I noted the clip was installed in the right orientation, and it appeared seated. 3,500 miles later, last Saturday night, I went to lube the chain in prep for a group ride Sunday, and the master link just happened to be visible when I put the bike on the stand, and the master link clip was gone. The side plate was still there.What factors could cause a clip, which appeared to have been properly oriented and seated, to come off? I bought a new peen-type master link.I know how lucky I am, and am going to give the shop in Houston a call tomorrow for a friendly chat.