I think you answered your own question ,leave it alone or you will just give yourself a big headache ,if you get that bit to fit it will probaly not fit elsewere . It might be worth asking if they fitted a lexus part or a pattern part ,and yes i know it should be a lexus part from a lexus garage but i have seen first hand how some garages cut corners and i bet if a pattern part is available it is a lot cheaper than the original.Also did the car have a shunt and if so has any thing else been damaged that is affecting the fit of the new bumper that has not been seen .