What happens in the shower.... STAYS in the shower...

Quick question for all the writers out there:
Why must we get all our best ideas in the shower?

I mean, seriously. First I'm scrub-a-dub-dubbing, belting out whatever lyrics I remember from High School Musical when
BAM!!!
That scene- that one scene that I've been trying to figure out for ages- just pops into my head and plays out so beautifully, and I'm miraculously inspired to write. My hand is itching to find some sort of writing utensil, but what am I supposed to do? I'm in the shower, and all I have in my hand is a bar of soap that has proved itself a good microphone substitute... But I'm not exactly sure it could be a good pen substitute.
Next thing I know, my idea is going down the drain and there's no way to retrieve it. My mood is ruined and suddenly I don't feel like singing anymore.
Is that just me, though? Or do other artists suffer from this as well?
Hm, I should find myself one of these!

That would definitely come in handy...