Sometimes, people are ridiculous. From the statement by the people affected, they felt that the sauce tasted weird. Not from the usual. If it tasted weird, why continue eating it? Just go back to the shop keeper and tell him/her that the sauce doesn't taste right.
I've seen a uncle at West Coast Food center, cook the Char Kuay Teow and he keeps the left overs in a pot and any customers who orders, he takes a portion of it and mixes with the new noodles. People still buy. People still eat it. Still tastes good. Besides, the cockles are always left exposed to the outside environment without any refrigeration.
If you go to HK and observe those really famous beef noodles shop you will see that they will scoop up 1 bowl of beef stew every night. The next day they will pour in that bowl in to the pot with the fresh ingrediants. The beef noodle soup sold to you could still have ingrediants from 30 years ago.