I do that a lot, too, presumign everyone likes and even knows everyone else can be a problem. But, I often go the other extreme then, too. Someone on Facebook wondered why someone didn't come to a funeral after later seeing them and the person offered condolences. Not realizing it might have been a rhetorical question (I'm famous for not picking those up ) I posted 5-6 reasons in response. (Sickness, started to go but car broke down, out of town, I forget the others.)
The person did say it made her feel better that I did that, so I guess it was okay.
As to yours, I don't think it's a social mistake unless you know, as above, it's for a small number or something. I think it's more the case that we need information we don't have, and it's normal to seek such information. Most people understand that not everyone has all data and will just accept it. It's actually, to me, one of those pieces of small talk where - as I note in another post - it's a little better if you provide a lot more data than usual, even it's actually normal communication pattern in such small talk to go, "Are you going to x's party?" "No, I wasn't invited/wasn't aware of it." Oh, sorry." "That's okay."