Assuming they find the key in an area where its obvious where your car is
If its at a shopping centre with lots of cars, chances are it will take him/her/them a while to try every car trying to work out which car it is.

Lots of "what ifs", etc. If you feel its right, just do it.
I was happy without a pad, i look after the keys well enough and wouldn't go out partying and drive anyway (ref: cousins!)