Don't forget external sources
grs is right about cross-reference and bits being set at the word level.
You can also go to the data table (looking at it with the Binary radix), and press the USAGE button. That will tell you if there is a word-level (a "W" in left margin) and also at the file level ("F" in the margin).
It's also possible that bits may be set by an HMI, SCADA or another PLC. You'll NEVER find those, no matter what search method you use.
Then there's indirect addressing. Searchin on B3/0 may find the contacts, but it will never find OTE B3/[N7:11]. The cross-reference may help there. After checking on the word address, scroll to the last part of the file listing (alphabetically, B3/[N7:11] comes after B3/999)