Doesn't find a lot of simple "words" and phrases

I have X1 ® Professional Client Version 6.7.3 (Build 4054dh); Windows 7 Professional 64-bit; Core i7 Quad-core I7-870 2.93GHz Processor; 8 GB memory; Microsoft Office Home & Business 2010; Norton Internet Security 2010
As for "word" searches (I sometimes put "word" in quotes because they aren't words in the literary sense, but rather alphanumeric strings of characters), I have special unique codes that I tag items with. As an example, I have a large (1808 KB) Word 2010 file named a1.docx in it with the following "words" in it (among thousands of other words):
11LAA 11LAC 11LAD 11LAI 11LAJ
X1 finds 11LAA and 11LAJ but it doesn't find any of these 3 words: 11LAC 11LAD 11LAI
So for example I search on 11LAA (without quotes) and it finds it
And I then search on 11LAC (without quotes) and it does not find it.
It did find these 2 "words": 11JAM 11HAV
It did not find any of these 3 "words" (again searched on individually and without quotes): N312LL N951DY N712AL
As for phrase search, it doesn't find any of the following (quotes included in the search string):
"wisconsin criminal"
"minnesota criminal"
But it did find
"2010 taxes working area"
Just to see if it was getting goofed up by Word 2010's format, In Word, I saved a copy of the file as "plain text (*.txt)". After being sure it was indexed, (and weeks later), I got the same results as above -- For some search terms I got a hit in both a1.docx and a1.txt, and for some searches I got no hit in either one of them.
I could go on and on -- it is hit and miss. Is this normal, i.e. is everyone satified with frequent false negatives?
Thanks for any help.
As for "word" searches (I sometimes put "word" in quotes because they aren't words in the literary sense, but rather alphanumeric strings of characters), I have special unique codes that I tag items with. As an example, I have a large (1808 KB) Word 2010 file named a1.docx in it with the following "words" in it (among thousands of other words):
11LAA 11LAC 11LAD 11LAI 11LAJ
X1 finds 11LAA and 11LAJ but it doesn't find any of these 3 words: 11LAC 11LAD 11LAI
So for example I search on 11LAA (without quotes) and it finds it
And I then search on 11LAC (without quotes) and it does not find it.
It did find these 2 "words": 11JAM 11HAV
It did not find any of these 3 "words" (again searched on individually and without quotes): N312LL N951DY N712AL
As for phrase search, it doesn't find any of the following (quotes included in the search string):
"wisconsin criminal"
"minnesota criminal"
But it did find
"2010 taxes working area"
Just to see if it was getting goofed up by Word 2010's format, In Word, I saved a copy of the file as "plain text (*.txt)". After being sure it was indexed, (and weeks later), I got the same results as above -- For some search terms I got a hit in both a1.docx and a1.txt, and for some searches I got no hit in either one of them.
I could go on and on -- it is hit and miss. Is this normal, i.e. is everyone satified with frequent false negatives?
