I frequently book jetblue on travelocity. I give my TrueBlue # when I book. They also don't allow seat selection. Then when I log into my account on jetblue.com the flight is listed and I can go in and select my seat.
(I'm not sure how long the lag is before it shows up -- I usually wait a day or two and it's always there when I check.)
Just booked a flight on travelocity. Less than two minutes later it was on my trueblue account flights page and I was able to go in and select seats.