LTSpice was made by Linear.com now part of Analog.com. Great $$$ were spent so you can have free software. It was never intended to help TI.com sale parts. And TI uses encryption so you can not see what is inside the part.
If you want to play with a buck PWM look at LT1765. You should have a jig "1765" that will get you started.
Right now it will work for 4-25V buck to 3V. It could be changed to regulate current.
For TI, I've used ones from the "general spice models collection" pack on this page.
You have to create the symbols for them in LTSpice, but the models work once you figure that out..