Do you have any backup, secret words or private keys that instant-e gave to you before it disapeared?
Without the private key (that can sometimes be recovered from secret words and backups), your only chance to get your LTC back is finding those guys and ask them to give it back.
I Got this confirmation mail from instant. Like in below attachement, where you can see that they write to me that they receive 13 litecoin in this wallet.
And also got bild from litebit with confirmation on which wallet money was sent.