Crank shaft bolt broke off - 2004 accord
 

I have a 2004 Accord EX 52K and have followed all service requirements. I had car serviced 3 months ago and yesterday the bolt that I think controls the serpentine belt snapped off.
Did my dealer tighten the belt too much. They mentioned I don't drive enough to keep it lubricated but this seems absurd.

Which bolt broke exactly?

Was it the one that holds in the tensioner, or the one on the crankshaft?

The serpentine belt tension on the 4 cylinder is self adjusting controlled by a spring. To service the vehicle there is a bolt you turn against spring tension to remove belt and do the same to install then just release. You title for your post mentions Crank bolt?

I attached a pic. Is it the bolt that is circled in green or red?