In the space of 5 mins, two of my answers from other questions have been upvoted and all because I asked a good question today. It's very flattering, I must admit, but are there safe guards in place to prevent someone upvoting too many questions for one person?
When a particular contribution made me curious of the author, I often look up what else the author contributed, and of course finding something valuable there makes me vote accordingly. Thus there is nothing wrong with upvoting questions or answers to items one gets to read only because one first read another question or answer of an author.
Of course, the upvotes should be deserved, but this can easily be judged by the upvoter within 5 minutes, so one need not be suspicious of two upvotes so close in time.
There is a script that attempts to identify vote fraud (both for and against you) and will reverse any that it detects. If your fan has over-done it or has acted too quickly (i.e. without reading the answers) these votes may be removed when the script runs later today.
The details of what constitutes "fraud" from the scripts point of view are not public information, but the hints I've gotten from the team suggest that they are not as simple as "counting".
See also: Attack on my account.
Serial upvoting is handled automatically and you don't need to get a moderator/Meta involved. In this case it's just two votes though, so I doubt it would be detected as fraud (it's usually many votes when fraud occurs, but there cut off isn't publicly known).
Basically, don't worry about it. In this case it's doubtful they had any ill or improper intent.