My guess is the alignment is simply out. There's a TSB on the ES about how to properly fix a pull to the right or left so they'll know exactly how to do it.
If they ask you to come back say "Yes, when can you schedule me with a loaner?" Keep in mind that these people are trained to deal with customers that are able to shell out $70,000 cash on vehicles. Ask yourself "Would someone who had just written a check for a $70,000 LS430 walk away without a loaner? Would they sit at the dealer for 5 hours?" The answer is definately no. Don't be rude or mean, just be stern and confident. You must maintain control with these people. You are a Lexus owner and you are very valuable to them.
Something most people don't know is that a dealership's service department makes a great deal more money than their sales department. The real money is made off of a customer in service over the vehicle's lifetime and in referrals. I own a marketing company and almost all we do is train car dealerships how to deal with customers and turn sales business into service business. On top of that training we sell them inventory systems, customer rewards systems etc to help them do that and track their sales. THAT is how important service business is to a dealership.
They get paid for the service the same whether they charge you or Lexus for it. Don't think they're providing you with "free" service, they are being paid for it. Part of what they are being paid for is furnishing you a loaner for your warranty work.