My wife's previous employers had a gloriously silly example of the earlier days of wireless proximity key fobs/cards. (this was in one of the Renault models.)
Essentially, the car was designed with a push-button starter, and unlike some of them, the key card only had to be near the car (they had a much more sensible version where there was a slot the card had to go into to make everything work) to start the engine.
You can already see where this is going. Sales rep has his key card in his coat pocket which hangs by his front door. Close enough for the car to register the card and be able to start, Goes out, starts engine, drives off. Leaves coat at home (along with card). The way those systems were designed, for safety purposes, once the engine was started you didn't need the card inserted/in proximity to keep it running. So he had no idea there was a problem. 200 miles later, he parks up, shuts the car off, and goes into work. 6 hours later he comes out, finds out he hasn't got his card.
Which is 200 miles away.
Nobody else had house keys to get in to get his key to bring it to him. You had to order the replacement cards from Renault in France so no spare. Unintended consequences indeed.