Whereupon the popular imagination naturally inserted an indefinite article to produce "me an' my baby in a 69 (the sex position)", forever sealing it in the memory vaults of a generation. You can't tell me it wasn't engineered that way from the get-go. The whole song may well be hung on the reference to the soixante-neuf. Certainly none of the pop hits of 1969 sounded like this crap, and the only reason it has to be '69 instead of, say, '66 or '68 or '64 is the rhyme in the first stanza:
[...] bought it at the five and dime
[...] it was the summer of '69
But you wouldn't buy a real guitar at a five-and-dime. It's outside the dime-store price-point. You'd buy one from an instrument shop, maybe a pawn shop, or (ahem) a music store, perhaps in the summer of '64. And that first stanza is the only place such a substitution would even change the song, because "nine" isn't even a recurring rhyme scheme driver. I could go on and on, but instead I'll simply refer to The Rock N Roll Hall of Shame's hit-by-hit indictment of Bryan Adams' career.
Anyway, back to "Kids Wanna Rock": Much more amusing if you sing along and change the lyric to "Everywhere I go, kids throw rocks". Because this is exactly how almost all my friends received this song. (All of us but that one kid who insisted that a charting pop song was by definition a good song, and who therefore creamed his panties incessantly for Michael Jackson. Same sort of intellectual roadkill who sneers that God and Jesus are "make believe", yet swallows the myth-story of the Invisible Hand of the Market without a hiccup.) Because that's how most of us felt about Bryan Adams: Musically forgettable, lyrically incoherent, a nauseating purveyor of synthetic nostalgia. We wanted to throw rocks at him, and at the music-marketing machine that foisted him on our airwaves.
Yet somehow, either the world forgot about wanting to throw rocks at Bryan Adams, or that twist on the lyric somehow stayed confined in my little teen social circle - because at least until now, if you Google the phrase "Everywhere I go, kids throw rocks" there are literally NO results. NOBODY, no blog, no forum, no 4chan, no comment troll, nowhere - has seen fit to brand that particular witticism on the interweb, at least not anywhere that Google can find it.