Even though you import the wallet, it will not stop what's happening or going on to the wallet, I know quite well that it will be difficult for the coins to be reverse according to the analysis Charles-Tim said, but from what you explained I believe that you have not experienced this kind of challenge before, because once you experienced this kind, you will believe that importing the wallet with help of your seed phrase can render help. This matter should be a matter of blockchain, since the value bitcoin did not meet up the preferred demand of the excahges it suppose to bounce back to the wallet, so what we suppose to do is to agitate to the exchanges that refuses to return the funds why it has not meet to the number or figure of bitcoin before it can be confirmed.
I get your point but it is you not getting my point, transactions are irreversible on the blockchain but with if they aren’t confirmed they can be spent to another address through the use of RBF and since RBF isn’t enabled on your transaction because of the wallet you use for sending them you can simply double spend which is possible for two reasons; first is because the transaction is still unconfirmed and secondly because most nodes have enabled default RBF so they can easily replace old transactions with new ones.
Now why you need to actually import your wallet is because your trust wallet isn’t flexible like this to actually switch nodes like the electrum wallets or other wallets, you can simply switch nodes and check which of the nodes has your transactions as local and then your can rebroadcast a new transaction with a much higher fee. Reason why you use a much higher fee is because the old transaction might still be in the memepool of other nodes so to with fee being the priority for transaction selection the new transaction is picked and confirmed, there by rendering the old transaction invalid. But as BitMaxz suggested if you check the mempool explorer and your fee is around purging fee rate then you can as well wait for it to be automatically dropped from all the nodes.
Or better still contact the exchange in question should the transaction drops but to me that process takes a longer time and in most cases it never gets resolved
FYI these days many node enable full RBF flag. That means you can replace any of your unconfirmed TX, even though it doesn't have RBF flag.
Yes I know, that’s why I even suggested the idea of double spending same transaction (basically RBF) as most of the nodes will just replace it with the new transaction since they have RBF enabled as default