I am a developer integrating Polkadot JS to my app. I am creating an offline transaction which I am sending via the Polkadot Api RPC. In return I get the txid, but it does not help me to retrieve the transaction once it is mined. I need to get the block index and the extrinsing index in the block that the transaction will be mined. I am using the HTTP provider, the websoccet will not work for me. Can you guide me in the right direction?