Revoked a PGP key, is there any way to get a revocation certificate now?

I signed up for Keybase some time ago, and at the time of registration Keybase created and hosted a PGP keypair. I never really exported or used that key for anything. Fast-forward about three years. I created a new PGP keypair locally with the intent to actually start using the new keys in earnest. I revoked the old Keybase-generated key via the web UI and replaced it with my new key. All is well.

However, I now realize that my old Keybase-generated public key ended up on pgp.mit.edu and the rest of the SKS network, and I don't have any way to revoke it because I never thought to export the old private key that Keybase created.

At this point, do I have any recourse? Mainly I'm looking for a revocation certificate that I can submit to keyservers to get the old key invalidated. Failing that, is there any way to export a copy of the first private key now that it's been removed and replaced?

I have a feeling I won't like the answer. But it couldn't hurt to ask.

No files or tests are named. Start by reviewing the described Keybase web-UI flow and how the original PGP key was created, stored, revoked, and replaced; done would require determining whether a revocation certificate or private-key export is possible and documenting the answer.

Written by the indexing model from the issue text.