Welcome Laksi

It is always slightly unfortunate to enter the community with a major complaint; one might think the posting is to "get even" with the airline/hotel company one potentially holds a grudge against.

Vueling seem to be saying that they are not responsible for calling flights - or maybe that you should have checked the screens whether anything had changed (which is a standard disclaimer printed on boarding passes these days); no idea how that works in Barcelona - I am fairly sure that they are often not calling in the US; if they are right you probably should complain with the airport, but maybe they are wrong; also twelve passengers seems a large number.

I don't know how this constitutes a security breach - this seems an isolated and certainly unexpected happening, and I don't think your average malicious passenger is hoping that his (they mainly seem to be male) luggage is taken and he wouldn't have to fly because of this type of incident.

I indeed would have expected the luggage to be unloaded - I assume so would the purportedly malevolent non-flyer. It happened to me quite a few times the last few years that my luggage was NOT on my flight, but on a later one - and I didn't find that out until I was waiting at the luggage belt.