Hi,
I accidentally sent LTC to BTC account. From GDAX/coinbase to some merchant. How can i get it back? Please help.
You can’t.
The only one who can get that LTC is the merchant, if and only if he has the private key to the BTC/LTC address you sent the founds.
Sometimes, merchants do use wallet as a service, so in that case shall the wallet provider be able to claim those funds.
LTC Address 375UxDMEuLaNgzBVgV1XRZxvK11jueDoY7 | BlockCypher is my transaction. I tried contacted the Merchant. They said they don’t have my money. They asked me blockchain and coinpayments. I am clueless 
shouldn’t have done this big step of buying ICOs while I was half asleep.
May I ask you more details?
Specifically, how do you know that is a Bitcoin address? Was there any way you could confuse it as if it was a LTC one?
Which merchant is this we are talking about? May be do you have any screenshot or URL to the payment page?
Well if it was really Bitcoin address then you’re out of luck, there is no way to recover that sent Litecoin.
Except if the merchant has the same address for LTC and BTC which is impossible to happen.
I’m sorry for your 4 Litecoin 
You are completly wrong.
It is possible to have same address on both Bitcoin and Litecoin, if they are p2sh (starting with 3).