I believe syg00 has had the best suggestion so far, ie read the man page.
Currently you have been informed that -f is to read expressions from a file, which of course we do not need here.
Again syg00 points out the last suggestion -R is of no use to you as you stated you only wish to search data in a single directory and no further.
I have a few suggestions:
1. egrep is considered deprecated although it still works and the suggestion is to use the -E option with grep
2. You have expressed you would like to return the file names, so may I suggest you look at -l (that is a lower case L)
3. To perhaps speed things up a bit, you ultimately only need to find a single match before returning the file so progressing past one is of no value, so again may I suggest looking at the -m option
Let us know how you go