I didn't (quite) catch that
Please repeat what you said; I didn't or couldn't hear you. A: "Do you need anything from the shop?" B: "What? I didn't quite catch that—the oven fan was too loud."
I didn't (quite) catch that (last) remark. and I didn't get that.; I didn't hear you.
I didn't hear what you said, so would you please repeat it. John: What did you say? I didn't quite catch that last remark. Jane: I said it's really a hot day. Bill: Have a nice time, if you can. Sally: I didn't get that. Bill: Have a nice time! Enjoy!