Your coins were not stolen.
If I understand correctly, liqui.io is an online exchange NOT A WALLET; thus, all the LTC you send to them are not yours, are theirs.
What you own when you send your LTC to them is a number on their database, and at some point in the future you’ll be able to retreive that number of (real) litecoins to your own wallet; odds are high that those coins you’ll get at the end won’t be the very same coins you deposited, but only same amount (and some other different coins).
What you need to do is