something that made me curious

[brooklynian]

What has changed is the value of the cryptocurrency (bitcoin) invested in, the money invested increases or decreases in line with the current value of the cryptocurrency. If the value of the cryptocurrency increases by 100%, your investment will equally increase at same rate and vise versa. The money goes nowhere.

[Akoldi_ibk]

It can be tricky thinking your money disappear but actually  it goes nowhere. What is at play is the change in price/value of bitcoin which determines the value of what you bought. As the price changes, your investment also responds in the direction of the bitcoin price.

[aminurrahaman]

If the A invests $1000 in bitcoin, then the next day the price of bitcoin drops dramatically and the A loses $1000, which makes me curious, where does the $1000 A money go?

I think you asked your question with an inappropriate example.

Let me clear your question with a right example:-

If A invested in bitcoin at price of $1000 that means someone sold his/her bitcoin to person A, cause you can only buy bitcoin or cryptocurrency when someone else sell his/her bitcoin or cryptocurrency.
Money doesn't go any where its just keep moving from one hand to another.
If you buy a piece of bitcoin at $100 and you sell that bitcoin at $1000 that means you profited $900, and that $900 comes from that person who buy your bitcoin at $1000.

The simple trading is totally depends on demand and supply if demand increase then price will go high and if demand decrease then price will go down.

[Ardavan2150]

the price has to zero for A to lose his money which is not going to happen!

generally speaking the money doesn't go anywhere. you converted your money to something that lost value. if you have trouble understanding how it works then imagine something more common like a new car that you buy and then have an accident with and its price drops, or when you buy shares of some company at $10 a piece and that company doesn't perform well and the share price drops to $9, your investment doesn't go anywhere it just would have a little less value. or the same way, if the price of it goes to $11 you didn't create money from thin air, that item you held is now worth more.
so when you sell it to someone else on the market in first case you lose a little money and in second case you make a profit.

I don't know if this is entirely true. Image I buy all the bitcoins there is. All the market cap of the bitcoin is then distributed to everyone who had bitcoins before. When the bitcoin price drops, my money is lost, and I am poor, but the money doesn't just disappear, the people who sold it to me profited. So the actual currency that is inserted in the crypto market has to go to someone else.

[medconindi]

Think back, if A invested $ 1000 in bitcoin, the next day the bitcoin price increased and A got $ 2000. Ok, you probably already understand.