He would come down laughing over something fearfully funny he had been saying to a star, but he had already forgotten what it was, or he would come up with mermaid scales still sticking to him, and yet not be able to say for certain what had been happening.

It was really rather irritating to children who had never seen a mermaid.
"And if he forgets them so quickly," Wendy argued, "how can we expect that he will go on remembering us ?" Indeed, sometimes when he returned he did not remember them, at least not well.

Wendy was sure of it.

She saw recognition come into his eyes as he was about to pass them the time of day and go on; once even she had to call him by name.
"I'm Wendy," she said agitatedly.
He was very sorry.

"I say, Wendy," he whispered to her, "always if you see me forgetting you, just keep on saying 'I'm Wendy,' and then I'll remember." Of course this was rather unsatisfactory.