I'd accept it

"Sir this ticket is for the wrong train. This is the A line. You're meant to be on the feline."

I imagine he just looked at the guys phone like:

blink blink

And was probably socially awkward about how to tell him thats not a train ticket.

While at the same time realizing that the cat looks socially awkward too. So this guy took a picture of his cat, while making some OTHER mistake that has the cat feeling unsure how to proceed.

Then he probably wondered all day what he said to that cat.

valid ticket. good day sir

So, did the conductor accept it?

The cat tax value alone should cover the cost of a ticket.

That could be taken as a threat.

I would kneel, and tell him to board with an honorific.