Debugging: what if you can't reproduce?

[amyjko]

After reading the chapter on “Debugging” a question rose in my mind. It was when the chapter was talking about reproducing failures in order to find out the faults so it can be traced back to the defects. I was wondering if there was any instance where you can’t reproduce a failure. Like the failure happened so suddenly (you were inputting random values) and thus produced the failure. Is this even possible and if it is, is there a specific example for it? I don’t know why, but as soon as I read about reproducing failures, it got me curious about if it was possible to never reproduce that same failure.