Wouldn’t it be good if we had the stats who locked the thread? I can't see it anywhere for now.
Not that it wouldn't be good, but it would be somewhat unnecessary since the subject isn't really a complex one and the answer is just one of two options, it's either the thread starter or a moderator that locked the topic; then again I don't really know how many people are actually curious to to know whether it's an OP or a mod that locked a particular topic, not much I suppose, so I don't think a statistic on that is necessary at all.
But you can assume by that yourself depends on what kind of thread it is, if it related to a query asked by someone and the answer was found then probably OP itself locked the thread to avoid spamming anymore.
And then if it's a spam megathread or a redundant topic, then it's most likely a mod. Makes sense.