Well, not the most high-tech of questions but still something that seems to confuse people... :o
$ grep -H -r "my text" /home/user
Only want the filenames, eh?
$ grep -H "my text" /home/user/* -R | cut -d: -f1
And if I know the filename or extension, what then?
$ find / -type f -print0 | xargs -0 grep -l "test"
Best of luck finding your texts...