Never lost a bolt but we actually had our chain ring bolts loosen-up on an out and back overnight ride this past spring. I didn't have a chain ring tool with me but was able to tighten the bolts with an allen wrench to get home. These were the bolts to the larger two rings. Yesterday as we will climbing a fairly long hill, over a mile, the drive train started making noise and the wife (Stoker) looked down and saw the granny ring was wobbling. We stopped and two of the bolts were loose but when I tried to tighten they just spun around and would not tighten. Not sure why that is happening? This is on a triple 9-speed Race Face crank. When I got home I tried again and they just spun loose and wouldn't engage.