You may want to read
Missing 10 Characters in WIF Private Key - Can I recover them?Judging by that topic, I don't think recovering 11 missing characters is (currently) very feasible,
unless you've made a transaction out of the address
or have a signed message (for instance to proves ownership back in the days). Both aren't very likely with paper wallets, but if you have one of those, you'll know the public key. Knowing the public key (not to be confused with the address), makes it much easier to recover the private key.
I am afraid you are correct.. blocks were mined approx 5 years ago with dozens of coinbase transactions went into it.
Should have kept wallet for each block mined, something satoshi have done and now I understands why.
Satoshi probably would never have to worry about it since in those days it was P2PK