If you have an inkling of your file details, find can locate it. I misplaced some files a couple of months ago. I knew I had worked on them on another machine and was pretty sure, a copy resided on my disk, somewhere.
I found a date reference to the files. It was all I needed. find did the rest.
I knew I had last worked on the files on 19 July. I calculated the number of days, using fingers and toes, and passed the number to 'find'.
It was 137 days since I last modified or accessed the file. Here's the find command.
find . -mtime 137 -print
find - the find command
'.' - start search in the current directory
-mtime - look at files last modified
137 - days ago
-print - print out results
Minutes later, I had my files.
You can search for files by name, using -name instead of -mtime.
find . -name *.gif
Searches for all gif files in current directory and sub-directories.