IF Statement with Three Conditions Including VLOOKUP

I'm trying to write an if statement that includes a VLOOKUP, ISBLANK, and ISERROR, AND separate sheets.

=IFERROR(VLOOKUP(F2,'Sheet2'!$S$1:$T$9999,2,FALSE),"Scrub")

The above formula is working fine except that when column F is blank it enters "Scrub". I want to add an ISBLANK statement so that if Column F is blank return blank. I know to get a blank return I enter "" but I can't seem to get it to work. I keep getting the too many arguments error.