This is waht their own website says:
Whilst theft is a criminal act, it is also a “tort” in civil law (delict in Scotland). There are civil law remedies available for the torts of trespass and conversion which arise from theft and damage.
A business invites its customers to its premises for the purpose of browsing and purchasing goods and services. When a customer enters premises to steal or damage goods or interfere with goods e.g. price swap or to procure services without payment, they are acting outside that purpose and are committing a trespass. Where goods are stolen this is also a conversion. Such acts are actionable in civil law.
A business employs staff to fulfil a specific role. Where staff steal or damage goods, or procure services without payment, they are similarly committing a trespass and conversion.
There is also contractual relationship between a business and its employees. There are usually specific terms in a contract of employment and there are further implied terms such as a duty of trust of confidence. These terms are breached where an employee steals or damages goods, or conspires to do so. Civil remedies are therefore available in both tort and contract where an employee causes loss and damage.
Where liability for trespass and/or conversion can be established, the wronged party is entitled to recover its losses which were foreseeable. Damages are available in respect of the goods damaged or stolen, and special damages are available for all other foreseeable consequential losses such as the cost of the disruption to the business, in investigation, security and administrative costs which naturally flow from the wrongdoing.
These are long established principles in common law (Judgments handed down by the Courts over hundreds of years). The principle was also reinforced by Parliament by the enactment of the Torts (Interference with Goods) Act 1977 (“the Act”). Both the common law and the Act provide for a wronged party to recover damages where there has been a conversion of goods (ie a theft), a trespass to goods, or negligence resulting in damage or loss to goods.
Any civil proceedings for recovery are entirely separate from criminal proceedings.
If you returned the wallet, they're on pretty shaky ground.