So that is telling me your log file is pretty much "empty". I don't know why it grew but it was likely some or more of the causes mentioned in my post above or discussed on my blog post category I linked a few above.
I would say shrink the log and grow it to a size that is appropriate with the VLFs in mind from that SQLSkills post and watch it closely over time to see when it starts growing.
Out of curiosity, before shrinking and regrowing, how many rows does DBCC LOGINFO in that database return? Still do the shrink and regrow with the VLFs in mind but just shoot out the answer when and if you get a second.
