Completely separate from any talks that I think parents have to have with kids (which isn't part of my answer to this particular question)...
I wouldn't jump to any conclusions. Kids of any age may have something like just to learn more about the product, itself. In other words, they can be curious about some "grown-up thing" even if they don't plan to use it immediately or even in the very near future.
My kids are grown now (one daughter and two sons). My reply wouldn't be all that different because my thinking is that there's some stuff that can be covered by any number of talks (including about values, good sense, future, etc. etc. - not just "the basics"), and finding stuff kids have tucked away somewhere can drive a suspicious-minded/worried parent crazy..
Kids will talk about what they'll talk about with parents, not talk about what they don't plan to talk about, and that's kind of it.
Not all kids will wait until they're even sixteen; so as far as I'm concerned, a sensible parent of a kid of either sex will leave (somewhere in the house) a little supply of this particular product; where kids over a certain age may be able to find them, learn about them, or - if it's going to happen anyway - use them (or at least share on with a friend they know should be using one).
The kid who just can't/won't ask one parent or other grown-up about, or for, that kind of thing just may feel a little more comfortable taking something he finds at home from a person he knows (or believes) won't think cares if he takes one/some.
You know how they say, "The road to hell is paved with good intentions"? Sometimes that road is paved by jumping to conclusions based on what someone "finds" among his kids' clothes/belongings.
"Worst case" , the sixteen-year-old daughter actually requires a partner to use that particular product. OR, is that really "worst case"?
To me, all the "talks" and conversation should really go on separate from what may be found in a kid's pocket or purse.