As soon as he could, Rolf dropped his journal and rushed to the park. While he knew very well where Luna would be, and while he knew he'd probably run faster as a tall human than as a small dog, instinct and force of habit kicked in and he switched to his animagus form as soon as he arrived.
And sure enough, there she was. Luna. His Luna, the Luna who knew about them and who had lived through their shared history. And she was wearing a wedding dress. He tried very hard not to look at this as a good omen.
He tried to shout her name, but since he was now a dog it came out as an excited bark instead. In his rush to get to her, however, he didn't even notice. All he cared about was to get to her before he woke up from the dream he was probably having and she disappeared again.