It's unforrunately common practice that many restaurants, to increase profits and/or reduce workloads, unethically and unhygenically recycle some leftover foods from previous customers, especially soups, especially hotpot or steamboat soups. Such practices can arise from any level within the restaurant (eg. lowly employee, manager, owner, etc), sometimes without the other levels being aware of it. Evidence includes toothpicks, tissue paper, etc, being found in soups.
[Singapore] - Diner finds toothpick inside fish maw soup during $450 meal at Jurong Gateway restaurant