They wouldn't inform you of stored codes unless they see an opportunity to make some money. I'm not saying that in an "evil corporations are jerks" way, just realism.
Anyway, that was a year ago, your check engine light could be something that happened since then (or, for that matter, something that happened while they were working on it).
No, the engine light has been randomly going on and off for many years now. Since I didn't notice any change in performance, I blew it off (and I didn't want to spend any $$ either). I also assumed (incorrectly) that it has been the same problem - probably a marginal sensor. Probably a bad assumption, though.
Funny thing is, on my (long) drive to NY this weekend, it came on again. If it's still on this AM, I'll get it checked.