I recetnly replaced the Wheels on my 05 but I had the same tires put right back on. It was done by a local Goodyear dealer. I specifically requested that they write down the "serial numbers/identification umbers for the TPMS sensors which they did. That way you have the numbers for use later w/o unmounting the tire. I also made sure that they put the sensors back on EXACTLy the same position on the car (i.e. RF on rgiht Front, LF on left front, etc.). In doing so, I hae not had any issues wiht the TPMS light coming on. I suspect that when the tires/wheels were put back on the car, the changed [position of the wheels and the TPMS sensors are no longer communicating to the ECU in the right "sequence" or with the right receiver. I'm not sure but I think the Lexus has twor receviers (one mounted forward for the front two wheels and one mounted in the rear for the back two.
Maybe someone else ont he Forum can confimr the two receiveers but I know for a fact that the sensors must go back in the ame places or they have to be "re-registered" (which is why the serial number is so important.