This sucks. We had thieves trying to steal a big ladder in the summer from our shed, but one of our neighbors turned on the light on the balcony and they ran away.
As for neighbors not seeing anything - this is quite usual. My coworker lives in a big apartment building in nearby city and thieves managed to steal all her money, jewelry and tech stuff right after her husband left for work at 11 am. She came home 45 minutes later and doors were busted. They struck hers and another apartment on that flat.
Main catch - those apartments were the only one without occupants that day and nobody else heard or saw a thing.
Cops managed to get a suspect - he was working with builders on facade renovation several months earlier and he had a lot of time with planning and observing targeted apartments.