Wrong theme accessed from post

In reviewing the http log from my site, I have seen some strange entries. I am looking for a possible explanation and an indication if they represent a security issue.

As background info, I am using a child theme of one of the standard WP themes – call it “a-child”. I have found a few entries in the log indicating that files from a different theme, call it “b”, have been accessed, notably style.css and images/search.png. According to the log, the referrer in each case is a posting (two different postings). But the same postings occur hundreds of other times in the log, without trying to get any files in the wrong theme. The source IP addresses are different, some of which look pretty legit and some cannot be resolved. The timing for each access is quite different. In one case, it looks like a normal session where someone typed in the URL for a posting directly; in the other cases, it looks like they clicked on a link to a posting from a third party site.

The thing is, there are hundreds of other accesses to the same postings without any GETs of files in a theme I am not using.

Is this a known issue? If it is not happening due to the URL being typed in directly, how could it happen at all?