The coin has disappeared from the wallet and never arrived in the wallet.
Although we often say (or write) that coins are kept in wallets, it is important to remember that this is just a convenient shorthand for communication between people.
In reality, Bitcoins do not exist in wallets, they are not stored in wallets and are not moved in or between wallets. Bitcoins do not really move between wallets and are not really sent from one wallet or arrive at another. This is all just hand movement and a very casual analogy.
Also, bitcoins are not stored in the blockchain. In the blockchain, only a list (a journal) of transactions with amounts of money using Bitcoin as a unit of measure is kept.
In summary, everything that is in the blockchain really happened. After about six confirmations, the blockchain is unlikely to change its view. If another person's wallet does not match the general and established view of the blockchain, the wallet is incorrect. Maybe because the wallet is out of sync. Theoretically, the receive address may have been entered incorrectly – but this is relatively unlikely.
Let's say you went into a shop and took a $ 20 bill out of your wallet and handed it to the shopkeeper, who put it in his wallet. Then the shopkeeper denies receipt of your $ 20. What do you do then? If you are lucky, there is a witness. The witness can not resolve your dispute, you must take him to court and ask the witness for testimony.
The blockchain is just your witness. The blockchain can provide evidence, but can not resolve disputes.
The transaction is still missing.
If it is in the blockchain, it is not missing.
If it's not in the blockchain, you still have the money.
Your transaction is in the blockchain and has 328 confirmations at the time of writing. 6 confirmations are usually considered safe. It is as safe as it gets. It definitely is not missing. The wait will not make it much more concrete, visible or undeniable. There is no chance it will disappear (on the brink of an unprecedented catastrophe and the possible end of the Bitcoin world)