You have no clue how committee's work do you? Committee's meet often, usually daily. Including when the Senate is in session. Member's will miss committee votes to attend floor votes, or vice versa. Member's very often misss votes because they've negotiated with the other member's - the outcome is already known.
See here to learn more:
http://thomas.loc.gov/r108/r108.html
http://intelligence.senate.gov/hr108.htm#May%202004