Hive Mac Wallet Migration
You're in luck, because I had a similar issue, and just finished making a tool to export private keys from old hive wallets. First, you should search your system for bitcoinkit.wallet, which is the file Hive used to store the wallet.

Then, go here and follow my instructions.
https://github.com/JesseCorrington/bitcoinj-wallet-export

Let me know if it doesn't work, I only tested this on my wallet, which was a non deterministic wallet with encrypted private keys. If you had a different type of wallet it likely will not work. Bug me if that's the case and I can see about updating my code.