I think it's perfectly normal, but I had a similar thing with Milo. I was the one who spent most time off work with him when we first got him and soon as my OH came home from work, Milo was ecstatic!
The first day I went back to work and OH had him, I got home and Milo took one look at me and then went and sat with his Dad! It really upset me at the time.
But now I think Milo loves us equally, but in different ways. I do most of the walking, feeding, grooming etc and all Daddy is good for is playing!
I think it's a bit like having children - Mum does all the practical stuff with a bit of playing, while Dad does loads of playing and winding up before bedtime!
I recently had a short stay in hospital which meant OH doing everything with Milo and in that short time he went from being a Mummy's boy to a Daddy's boy, all within the space of a few short days.
Once I got more involved with him again tho and OH back at work, things are soon back to normal!
I do think Denise has got a good point too, it would have been awful for my OH if Milo had been really down in the mouth while I was out of action.