Never attribute to malice that which is adequately explained by
- Hanlon's Razor
This saying is pretty useful for a couple of reasons in office politics.
First, unlike some other arenas, accusations in Office situations often make the accuser look worse than the accused. Perhaps especially if there is no data or proof and, let's face it, even if there were trusting the SysAdmin who is accused to find that proof for you is pretty unrealistic.
Additionally there's this feeling when you accuse someone of something that can be explained in other ways. It's pretty hard to pin down in words but it comes down to the idea that the person who accuses others of making them look bad is defensive for a reason. It's a weird kind of victim blaming now that I reflect on it. If I say that Myles "is trying to make me look bad by deleting my work!" the reality is that the first thought for a lot of folks is "What is Ananci doing wrong that someone would want to make her feel bad?"
About the only differences between an episode of Game of Thrones and typical office politics is the amount of nudity and the number of dead bodies at the end of the fiscal year. It doesn't have to be like this. But once you get to the point that you are suspicious that someone is explicitly doing things intentionally in order to damage your career - this is what it is.
All that aside what should you do about it?
Kill them with kindness and appropriate actions.
What does this really mean?
Don't ever acknowledge that you think Soandso is working against you. As far as you know, and you could only know so much not being their supervisor, they're doing their job to the best of their ability. If things are not done correctly then, surely, it was just a mistake or a process failure.
Your responsibility in this is to follow the best practice as laid down by your job. If you came across missing production documentation and you didn't suspect this Sysadmin of wrong doing, what would you do? Ideally you would open a ticket or in someway report the issue. It's not your job to speculate why or how it happened unless all the systems involved are under your control(or you are in a supervisory position). Why? Because you have no information about it beyond what you know (which is that the documentation is missing.)
Ultimately the best way to handle this sort of situation is to do your job and follow the expectations set by your company's processes. If you notice oddness, report it regardless of whether or not it is suspicious to you. Report dispassionately and only offer information that is pertinent and provable (for example how you discovered the missing data, the process you used to access it, the systems you accessed.)