Abe's curiosity could take him in a variety of directions. And being as this was quite a amorphous city he never ended up where he thought he would. It would be infuriating if he had anywhere to go but, fortunately, he had no obligations at all.
But the scene he stumbled upon ended up to be more fantastical than anything else he would have purposely been meaning to go. He watched a bit, silently, both subjects having their backs toward him until the frog resituated itself.
"Excuse me," he said, suddenly aware he was visible, "Miss? Are you conversing with a giant, purple tree frog?"
Perhaps this was to inject himself into conversation more easily or perhaps it was to confirm this whole thing wasn't a hallucination.