yuki father was never mention before, but after this chapter i got the idea that maybe he left before know that yuki mom was pregnant. In the worse case he left when know yuki is catalus.
That's my guess as well. I don't feel like the other possible explanations fit as well as that.
Other than him dying before Yuki was born/she could form any memories of him. But if that was the case i would have thought it would have been brought up before.