Search may be case limited

I have a wildlife telemetry database (24,000 references) that includes about 500 references that are related, but slightly off the topic (each of which has “NOT TX” as a keyword).  This morning I wanted to go through the chronologically oldest telemetry papers one by one without wasting time on the off-topic papers.  So I did the following two-line search:

 1.               Keywords         Contains        *            (this will collect all the references, but is necessary because you can’t do an exclusionary–“Not”–search on the first line.)

  1.   Not        Keywords          Contains   NOT TX    (this should have eliminated the papers that I wasn’t interested in).

I got a message box containing a tringle with an exlamation point and the phrase: " No matching references found."

After about an hour of trying different things, I discovered that using lower case (i.e., " not tx" instead of " NOT TX") in the second line gave me the result I was looking for.  But I could do a one line search (Keywords Contains NOT TX) for the  upper case term with success.  Weird, huh.

So if EndNote search tells you that “no matching references were found” and you you know that it just isn’t so, try lowering the case.

I hope Leanne or Jason don’t come back and tell me that this is described on page 1 of the manual…

Not going to say that, because it sounds like a “feature” to me! (who is just another user, unlike Jason!)

Because it does work for

* (in author field)

(“and” in dropdown) NOT TX (in keyword)

but not for “not” in dropdown… and you are right, it does work if you enter it in lower case and selecting Match Case or Match Words has no effect, nor does changing “contains” to “is” or "starts 

and it works if you do a Keyword search for NOT TX (match Case on) and it returns the correct entries. (NOT TX but not a record with “not tx” if match case is ticked and both if it isn’t ticked.  

So the only workaround is to use the “Omit from showing references” those records that have keywords contains NOT TX (matched case or not)  (or search for lower case as you found, which is probably easier unless you did want to distinguish “NOT TX” from “not tx”).  

but this is obviously a bug.