You can also import your 12 recovery words into other wallets that support the BIP39 standard, such as Electrum, Exodus, or BlueWallet, to see if your balance appears there.
The private key in question is "
imported" so, even if he restore that 12-word (
BIP39) recovery phrase to other clients, the imported private key will not be recovered alongside with it.
Read OP's last reply since it has a quote containing an important note regarding that:
"Imported funds are not protected by your Recovery Phrase. To ensure these funds are secured, please transfer them directly into your wallet."
Anyways, it could restore the wallet containing the imported key when restored in their own website/app since they link an existing WalletID and wallet.aes.json file if "
something" from the restored recovery phrase matched.
But that's not what OP need since he already found in under his imported private keys list.
The current outstanding issue is how to spend it as cheap as possible.