Exhaust bolt broken.

[Icarus]

so this is the story I was riding down us1 the other day when all of a sudden my 1993 xj600 secs 2 starts being extremely loud like my exhaust fell off. I drove her home couldn't see the problem after I let her cool I noticed the nut and bolt ( one that comes out of engine block to hold exhaust clamp) had broken clear off. all nuts are tight don't know how/why it broke or how to fix it. any help would be appreciated.