There is a plethora of things wrong here that make it almost impossible if not impossible to receive your Bitcoin Back.

1. You must know who you send the Bitcoin to in order to contact them, if you don't know who they are, you cannot find out their identity (pretty much), because Bitcoin is supposed to be anonymous and its near impossible to find someones identity from a wallet address (pretty much impossible)
2. The Blockchain is completely transparent, you can see all transactions ever made, so if you sent any Bitcoin to a wrong address, you could see to what address you sent it to.
3. Even if you knew the address, like I said in number 1, you would have to have their contact information and ask them to send the Bitcoin back to you
4. The person you've sent it to might not want to send it back to you, if you somehow get their contact.
5. that wallet address you sent the Bitcoin to might be inactive... in other words you (dropped it into a black hole that gobbled it up forever, or) sent it to someone's old wallet they don't use anymore/lost/deleted or will never look at it and it will always remain there, unspent, forever.