question about investigations and pay

What is the name of your state (only U.S. law)? colorado
If you are calling a nurse back to the workplace on her day off (as she only works the weekends) as a part of an investigation initated by a patient compliant do you have to pay her to return for the investigation or subseqeunt disciplianry action?

Probably. But why wouldn't you? How much could it be, an hour or two? I wouldn't take the chance, just pay it.