Theft can be hard to establish in a situation such as this and I doubt if the police would really be interested in a low level allegation such as this.
Much easier to eject the people concerned from the lounge citing breach of membership/entry conditions and follow up with a warning that a repeat will see the total forfeiture of any points/benefits etc of their airline membership and being permanently banned from all of the airline's lounges.
Yep, that sounds like treating it as theft after it has been reported to the airline
Still, I wonder what the police guidelines are regarding what they do and don't respond to, when it comes to petty crimes.
A rock through our front window when no-one was home? No. Theft of $50 through a fraudulent online transaction when the identity of the person committing fraud was known and could be verified? No. Theft of phones when their locations can be tracked? According to news reports, no.
On one hand, I can understand this, as these situations would involve a lot of hassle and time spent for cases with no real danger to the public and a low chance of any conviction, but on the other hand, it seems to leave plenty of scope for a determined thief to get away with a lot, as long as it is done in small doses and without violence.