my car is not in storage and used daily
it is not garaged either,parked on the road outside the house.
get the feeling it(rodent) must have crept in from underneath the car along some channel that leads into the trunk.(the trunk floor is at least 2 feet high from the ground)
the car did have some rear end damage some years back,when it was repaired by the previous owner via insurance.-maybe some seals are missing somewhere and let the pest in.-
will have investigate further.
for the time being, i have resorted to a mousetrap in the trunk baited with bread and let us see what happens overnight.