...you are in a serious moment talking with someone, you hear a weird sound in the background (like a crash or something). Your brain start thinking about the sound, and you think something like "oh my... I'd like to record that lovely noise!". When the lapse finishes, you realize that you stopped to listen the person in front of you and now you don't know what to saynow.
...you're working building something with a drill, and it gets burned and you see sparks. You think oh, great sound! Press the trigger again and hear the sparks again. You go for your recorder, press record... and there no sparks anymore. Now you realize that your drill is broken and you can't continue with the initial plan.
...you think about masking of different sounds in your environment, something like want to have faders for everything or a MUTE button to shut up your neighbors.
...you're with someone, an airplane passes by, and you say something like: hey, did you hear that nice doppler, dude!?