How does it happen? Quite easily it seems.
A few years back I visited Death Valley National Park via Las Vegas. So bear in mind my traveling companion and I had to fly from Miami to Las Vegas, then drive to Death Valley. This was in April, not the hottest time of the year, but quite warm.
After finally arriving at the hotel in Death Valley, my companion—my father-in-law—plopped his suitcase on his bed, and flipping it open we both fell dumb, mouths agape! There was a good-sized brown anole staring back at us, all the way from Miami.
These lizards are an established, breeding population in Florida, but non-native. So the stowaway had endured a long trip of the following hardships:
• Jumped into a suitcase in Miami, probably in the house.
• Endured the heat and lack of airflow that luggage encounters on the Miami airport tarmac and baggage system.
• Survived at least 4 hours in the cargo hold of the plane with low oxygen and likely very low temperatures, unless it was coincidentally placed in an area with animals being transported, which would have been heated and ventilated.
• Further endured a drive of about 3-4 hours in the bag, in the sun-baked trunk of a rental car.
The responsible thing to do would have been to dispatch the non-native upon its discovery in Death Valley. But I couldn’t do that.
We both realized it could never long endure the aridity of Death Valley, being a tropical/sub-tropical animal, so releasing it would be more of a death sentence for the anole and no threat to the environment.
The hotel was girdled by a lawn, heavily irrigated. The grass itself was likely non-native, living only through human interference and heavy watering.
So we placed the travel-weary anole on a tree branch above the lawn, gave it a capful of water, and left it alone, knowing it could never spread beyond the irrigated hotel lawn.