I was deciding on a name for my pet (a female baby symurgh) when I accidentally pressed OK and the naming slot vanished so I can't rename it. Can anyone help?

Your pet is not Nameless but has empty name which you submitted. Only pets with name "Nameless" can be renamed. We're already aware that there's a missing a check for an empty name, it will be added with the next update. I renamed your pet back to Nameless so you can give it any other name. Sorry for the inconvenience.