CINAHL default search doesn't search the abstract?!?

OK, so if you're searching in CINAHL, and using a combination of Headings and keywords, the default setting to just search a keyword is "Select a field". I recall someone telling me that this was not an optimal search, but didn't realise how bad it was until today.

So, I had this:
S7     abscess*     7,986
S6     (MH "Abscess+")     5,152

Combined it with the rest of my search, got 28 results.

Then, I looked at my other search terms without the Abscess terms, which meant that there were 93 articles. However, one of those articles had the term abscess in the abstract. In fact, it appeared several times in the abstract and was obviously a significant part of the study results!

So, I searched again, and this time I received fewer results!

S10     TI abscess* OR AB abscess*     6,000

But when I combined them with my other search, there were more results, including the one which I had found.

The really weird thing is that when I tried S10 NOT S7, there were zero results! How is that possible?

Weird, weird, weird.