How long ago was that drink?!
After 6 years of sobriety, I started off having 1 drink one night. And then a month or 2 later, another 1 drink. Then a trip out of the country - BAM, a full alcoholic blackout.
So no if it was just 1 drink, I'd say he can still claim being sober for 10 years, but I find it hard to fathom that one drink would be "enough". For me, the 1 drink I had confirmed that the sky didn't fall and my life didn't implode so I must certainly be cured. I proved to be very wrong on that front.