White patch on my 3.5mos daughter's upper thigh/hip area - SUPER ANXIOUS!?

Check her for meningitis. Get a clear gl and run it over the patch and if the patch stays there with the pressure of the gl you should take her to hospital asap just to be on the safe side. That's a good sign then, usually with meningitis you get patches and if you run a gl over it and it does'nt disappear then you know there's trouble ahead. My sisters son had meningitis and the same thing happened but luckily the week before i watched a program about meningitis and what to look out for and what to do if you suspect it. I was glad i watched it after that.