As a crew member it wouldn't have bothered me a bit, just put the critter in a little box with air holes, a wet sponge for water and stick it in your carry on. No biggie.
...and if the little rodent somehow gets loose during the flight (because, e.g., this ditz takes it out of the box to stroke), and can't be found / retrieved - why, I'm sure that you wouldn't mind being held personally liable for the cost of evacuating the aircraft and grounding it until the little dickens can be recovered, would you?
Regards,
“stick it in your carry on”
That might work until they close the terminal from what they saw in the x-ray. That would have got their attention.
rwood