Vista Marina - Theft of property, non returned deposit, allowing unauthorised access to hotel room

My daughter and a friend booked an apartment with vista Marina, Portimao. They were away for one of the evenings, the hotel allowed a group of males access to the room without their permission. Some of their property was missing upon their return. They were also surprised that their facilities were clearly used (beds slept in, etc). When they complained the hotel denied this and denied allowing them access to CCTV which could prove this claim. The hotel also witheld a partial amount of the security deposit. As the hotel gave access to unregistered people, they have no right to claim any damage was done by the actual occupants who paid the security deposit. They assured the staff no damage was made by them. The hotel clearly lacked any safeguarding or basic duty of care to the occupants of the room by allowing a group of males access to the room while the females were off site (luckily as they may have been attacked). When they complained no mention of their red book was offered, but they were met with hostility and denial of any wrong doing despite photographic proof from the males that they had access to the room in their absence.