Disregard. Sorry, misunderstood your question.
From the bash man page:
A non-quoted backslash (\) is the escape character. It preserves the literal value of
the next character that follows, with the exception of <newline>.
So using -F\t would split the line on the letter t. You can use -F'\t' or -F\\t
BTW I agree with grail's statement in your other thread about quoting -F.