The 27-year-old had locked up the glass shelves and cabinets at the shop at Block 449 Clementi Avenue 3 last Friday afternoon before heading to a washroom at a nearby coffeeshop.

However, he did not close the main shutters of the unit.

When he returned about 20 minutes later, he discovered that the shelves had been forced open. Three second-hand mobile phones and 42 top-up cards were missing.

Staff at neighbouring shops did not notice anything amiss.

Anyone with information can call the police hotline on 1800-255-0000.