Simplistically, lets say that pensions and putting money in the Bank are the same thing. So, you put $100 in the Bank. The Bank then uses the $100 to buy a golden chicken; now the Bank has a golden chicken, the farmer has the $100, and the Bank owes you $100. The Bank expects the golden chicken to lay golden eggs, which it can sell. But instead the golden chicken dies, and no-one wants to buy a dead chicken.
Now the Bank has $0, and owes you $100. You can no longer withdraw your money from the bank, it has "disappeared". The farmer has the $100, it still exists, but the Bank has lost it. Saying that it has "disappeared" is a way to shift the blame away from the Bank.
The joke is when you realise that the farmer isn't a farmer, he is an investment banker. And he got a $100 bonus. And he actually works for the Bank.
Now the Bank has $0, and owes you $100. You can no longer withdraw your money from the bank, it has "disappeared". The farmer has the $100, it still exists, but the Bank has lost it. Saying that it has "disappeared" is a way to shift the blame away from the Bank.
The joke is when you realise that the farmer isn't a farmer, he is an investment banker. And he got a $100 bonus. And he actually works for the Bank.