Re: Hypothetically if your daycare provider.....
Pediatricians are NOTORIOUS for under referring kids. Your DCP sees your child EVERY DAY usually. You're ped for 5 minutes a few times a year, if that. If an experienced DCP raised concerns with me, I would absolutely listen to them. It was my SIL (my daycare at the time) that first raised concerns about DD1, and guess what, she's deaf.
It will depend on the parent. I think as a child care provider I would expect you to raise any concerns. Some parents will listen. Others will think you're nuts. But at least you did what you could. Maybe mention casually there are many free state programs to get testing just to be sure. But if parent isn't interested there's not much you can do.