Not sure if you are in Cambridge MA but why not give Angell a call and just ask them if you need to bring him in sooner - maybe they will give you some info! Or call here at OSVS in RI, they will prob answer you if you call.
Also just an aside - the frontline lasts for more than 30 days so if you gave it to him on 9/1 you are probably still ok plus the fact that the tick was not attached for the req'd 48.
I'd still call for reassurance tonight
