Depends on the wallet that you're using and the reached number of addresses:
In case you don't know, bitcoin core generates a pre-determined number of addresses when you first created this wallet and stores it in the keypool. Bitcoin core will take address from here every time you need a new address to use until it used all of it. After you used up all addresses in your keypool, a new set of addresses will be generated for you. The max number of addresses in keypool is 100 by default.
IIRC - Try starting with the '-rescan' flag (Bitcoin Core). This may display it. For me, an addresses popped up during a test when I had used the '-reindex' flag.
the address has to be in your wallet, cause it will give you access receiving the coin...!!!
This post is useless.
I believe that you need the wallet address in your wallet.dat in order to have access to your Bitcoins.
You obviously don't know how Bitcoin Core generates private keys.