Dad: [on the phone] Did you leave your toothbrush here?
DK: I don’t think so… [moment of horrible realization] Are you looking at a pink case?
Dad: Yeah. Actually, it’s a bit bigger than a toothbrush–
DK: DON’T LOOK IN IT. It’s, uh, a fairly personal… feminine… thing. I’ll pick it up tomorrow.
Dad: [puzzled, but willing] Okay, sure.
I AM SO EMBARRASSED, INTERNET, I AM NOT SURE I CAN BRING MYSELF TO TELL YOU. But I will, because you will laugh. The pink case does not contain a toothbrush. It contains one of these, a stand-to-pee device designed primarily for women, but also incredibly useful for transguys who want to practice that whole standing-to-pee thing without shelling out $50 for a pissing-packer (by which I mean a packer that you can also pee through, like one of these).
I was dog-sitting for dad last night. I took the case out of my washbag when I brushed my teeth, and must have left it by the sink. THIS IS NOT HOW YOU REMAIN STEALTH, SELF.
*headdesk*
I’m ninety per cent certain that “it’s a personal… feminine… thing’ is still going to garner a few awkward questions, even if he doesn’t look in the case. (Which is seriously bright pink. The company sells the actual STP’s in cool colours, like ‘Nato green’ and ‘desert sand’, but hasn’t extended that to the carrying case. OMG!pink is your only option.) I have no idea what I’ll say.
I suppose I could switch topics to a discussion of the, ahem, dodgy looking DVD in his DVD player.
(L)earned Masculinity 
The pink case is camouflage for the Nato Green Urinal Stream Relocation Device, it’s a top secret piece of equipment, dangerous and embarrassing for the Top Brass if it’s allowed to fall into the wrong hands!
Er, yeah!
*Makes a bunch of Kung-fu poses and disappears*
I got one of those piss/pack things. Still haven’t used it yet, though it’s fantastic for utterly disturbing your mother!
I promise to be properly sympathetic as soon as I get back from the hospital, after I laugh myself sick. Ahahahahahahahahahahahahaha!
No, really.
*puts on serious sympathy face*
Ahahahahahahahahahahahahahahahahahaha!
Could you pass it off as a moon cup? Or tell him what it is and explain you wanted to practice at home before trying to use it in the OMG tiny! airplane lav, which is what you bought it for, seeing as you have an upcoming transcontinental flight?
Because seriously, airplane lavs were built for gnomes, as far as I can tell. Any right-thinking person will understand not wanting to sit down in one.
Failing that, I like your DVD misdirection plan.
They’re endorsed by Fern Britton of course it’s bright pink *somewhere* :p
He’s going to think it’s a gigantic pink ‘marital aid’ isn’t he? You have to tell us if he comments on it.
(Ps – Me and Ash have come across a dodgy DVD left in there too. Ash was flabagasted and told me that if he ever had to resort to that while we were living together then my ass would be dumped faster than I could say ‘Is she over 18 darling?’. (They might not have been his exact words – he was a bit less susinct at the time…)).
I seriously doubt that he will either A) look at it, or B) ask you about it. Why? Because you used the words “feminine things” When a men hears those words, he does not think “prosthetic peeing device,” he thinks of two things: periods and sex. If there’s anything a father does not want to think about in relation to his daughter, it’s those two things. Come to think of it, he probably doesn’t want to think about how you pee, either.