I think this happened to everyone, it's not a glitch, it was something with the server (I THINK). But if u ask an Admin or a Helper, they'll gladly spawn them back in for you.
We are very sorry for this. If you ask a staff member (and of course it's a realistic request) they should be able to spawn them back in for you.
It seems that when the server crashed last night, everyones animals got cleared again. We are sorry for this, again, and like Amanda said any staff member will gladly respawn them in on request.