I deployed a contract yesterday which was mined and which was responding to calls. Today the contract "does not live" anymore. Do I need to redeploy? Is there a way to find addresses of contracts I deployed with a specific account?
The easiest way to find your contract is to checkout out the account that created the contract in a blockchain explorer.
You may have been using a different network, like a testnet or tool. Or if you only interacted with the contract on mainnet for a brief moment after it was mined, it's possible there was a blockchain reorganization.
If you used the testnet you can search for the contract's address (or the address used to broadcast it) using etherscan's testnet site. If it doesn't show up as a contract creation transaction then the contract was never deployed.
If it was deployed you need both the address of the contract and the ABI (for example this is the ABI for the DAO contract).
Using these you can open geth from anywhere and have a local instance of the contract with:
var abi = JSON.parse(contracts_abi_string); var myContract = web3.eth.contract(abi).at(contractAddress);
You can then interact with