I have roku Ultra LT model 4662rw and can not find a button on top for lost remote??
No, it doesn't sorry. That's one of things that's sets it apart from Ultra.
Since roku Ultra lt model 4662rw doesn’t come with lost remote locator button; is there a app or truck anything to set one up
No. This function is activated by a button on the unit, there is no software control. The LT is a lower priced "light" version specified by Walmart with several differences from the straight Ultra so as to lower the price: