H.W.
It's just something that happens in phases for a while. For years, I was the go-to person for Kiddo; now, he would rather have daddy all to himself if possible-- but when he gets upset, I'm the person he goes to. (Not that my husband isn't sympathetic, but more that he has a 'masculine' relationship with his father and doesn't want to lose face, if that makes sense.)
So, I wouldn't read too much into it. Kids just do this. I have seen this a lot in the years I was a nanny, too.
I think as long as we aren't dropping everything at the moment our kids want us, it's pretty harmless. Just a momentary preference.