I was looking for a specific file using whereis from the command line.
I got a rather useless result, but I then found the exact file I was looking for by manually searching.
I did not make a mistake in the command line. Why didn't whereis turn up all my files? Is there another method?
whereis doesn't locate files, because whereis command is not intended to be used for that.
From whereis manpage
whereis - locate the binary, source, and manual page files for a command
whereis locates source/binary and manuals sections for specified
files. The supplied names are first stripped of leading pathname
components and any (single) trailing extension of the form .ext, for
example, .c. Prefixes of s. resulting from use of source code control
are also dealt with. whereis then attempts to locate the desired
program in a list of standard Linux places.
For more information type man whereis in your terminal to refer the man page. For finding a file you have to use commands like grep, find, locate, etc...
