In a Hostel dorm in Hanoi a few years ago, me and two friends. Woke up one morning to the foulest fishy smell, only difference was a new backpack was rested up against one of the beds which had been empty when we went to sleep but there was no owner to be seen. We opened all the windows, told the staff on reception and got out of there as quickly as possible and returned a few hours later. My two friends immediately checked out and moved elsewhere but I was skint and we only had one more night before moving on anyway so decided to stay. Met the owner of the bag and was chatting to him, expecting him to explain and apologise for the smell. When he didn’t I had to bring it up. Turns out he had no sense of smell so didn’t know how putrid it was but had been disappointed when getting off the night bus from Hue to find that his bag had got very wet in the luggage compartment under the bus. It had been next to a polystyrene box transporting fish, which had somehow opened and spilled all over all his belongings. Everything reeked and he didn’t even know, poor guy I reckon it would’ve taken a couple of washes at least to get it all back to normal.
TLDR - bad fish juice soaked into an unaware man’s clothes and belongings