I work in the software industry in a junior capacity and have been unable to reproduce a bug.
This issue has apparently been seen < 3 times at a customer site, and a senior member of the team have heard of it, however they have not been able reproduce or isolate the cause. Unfortunately I have not been provided any logs.
We normally close off such a bug with the stated reason "unable to reproduce". I have spent more than 2 days digging through code, comparing versions, attempting to reproduce this bug by following the given steps to reproduce. Unfortunately with no more additional useful information at hand, I don't see or know of anything else useful I can really do.
My manager has suggested I try different things than what was given in the steps to reproduce, to try and reproduce the bugs behavior I have to, no avail. My manager at the least wanted an answer to what possibly cause it. (This makes me somewhat uncomfortable as what "might cause it" when that can be definitively tested quickly, it either will or won't)
I would like to provide a satisfying answer to my manager, and frankly I don't have one. My manager believes that if it's happened twice on a customer system (but no useful logs pulled or available to me) that it is bound to happen again (I can agree with that however without additional information I don't know what to try), however I have been unable to reproduce this bug.
My work on the bug has the same conclusion as the senior member who has heard of this behavior (couldn't reproduce or isolate the cause).
I don't want to spend anymore time spinning my wheels on this as I feel I've given it every reasonable effort with the information I've been given. Is there a good way to sell this to my manager?
Clarifications:
The system at hand is a deployment of our companies software solution for a customer. I don't wish to go into anymore detail into this, my apologies.
By no logs I mean that no logs were provided from when these scenario(s) happened. Our code logs errors, warnings, etc. We have in my opinion decent logging.
In my opinion the bug's severity should be low to medium. The client has to wait longer to see the resolution of an action, however I still defer to those around me who know better than me, still want to see this addressed.