It is estimated that this restaurant is not big or business is not good. Mushrooms are sour. After the dried mushrooms are soaked, they have been left outside for a long time, and the temperature outside is relatively high, sour and stale. Generally speaking, it is not advisable to soak mushrooms too much at one time in late summer and early autumn (maybe the business is not good enough). If the soaked mushrooms are not used up, they will not turn sour in the refrigerator.

If the evidence (beef rice with mushrooms) is still there and you bought it today, you can report it. If the meal has been eaten or left for a long time, there is no way out, and you can only change to another restaurant for consumption in the future.