1.Why does this happen?
This kind of thing rarely happens, usually because users lack basic understanding of blockchain: there are many blockchain, and the same currency, such as USDT, will be issued on many chains.
The Tether USD(USDT) issued USDT details: https://tether.to/en/transparency/#usdt
You can find “On Tron”, “On Ethereum”,”On Solana” and so on. Your partner receive USDT on TRON, but you transferred the USDT on Solana, the error happened like this.
So be sure not to choose the wrong chain before you transferring money.
2.How to get my coins back?
Since Dolphinwallet is a decentralized app, this means that the account control and ownership belong to the user. You can follow the following steps to retrieve the money:
(1) Find your Dolphinwallet’s Mnemonic phrase (12 english words), Be sure to back up your mnemonic phrases, it is very important!
(2) Import the Mnemonic phrase to other wallet (such as metamask), Be sure to back up your metamask’s mnemonic phrases, it is very important!
(3) Switch to correct Chain.
(4) You can find you coin displayed on the other wallet’s list. if you can’t find it , you should import the coin first.
Good luck.