In my everyday conversations when trying to confirm an understanding or recall a piece of information I am sure I had heard before, I often use (そう)だっけ、だったっけ、and でしたっけ when speaking to equals or 目下の人。 But when talking to 目上の人 I'm never quite sure what the equivalent expression would be. I know that でしたっけ can be used with 目上の人 depending on your relationship and the situation, but I am trying to find out if there is a polite(r) equivalent※.
So far I've been given ~かね as a candidate from a native speaker. But since it was the only candidate and it doesn't carry the feeling of "trying to remember" I am inclined to think that there is no polite equivalent.
On top of that, depending on the situation and listener, it could be taken like you are doubting the other person, being condescending, or lack class(品)。Here is the site I got that from.
So, to sum up my questions: Is there a polite equivalent※ to っけ and if so, what is it? If not, what do people say when trying to recall a piece of information that they are sure they once had when in a situation where they should use keigo?
※By equivalent I mean carries the same nuance and feeling, not just in meaning as in "can be used to form a question."
Let me give some examples so I can explain the way the words "feel" as I understand them. The different meanings may or may not require different intonations. Also, I am not going to exhaust all options.
これはあなたの車だっけ?
1) Trying to remember if this is his car or not.
2) Expressing disbelief that this is his car. Both very casual.
これはあなたの車でしたっけ?
1) Same as above, but more polite. However, I highly doubt a regular worker (please assume properly educated, polite person) would say this to their 部長. This is the reason I posted this question.
これはあなたの車ですよね?
1) Expressing conviction that I know this is your car, but I want confirmation
2) Could also be used accusatorially
(I think there would be a split opinion about whether this could be used with a 部長)
これはあなたの車ですかね?
1) Used to ask a plain old question
2) Could sound like I'm being condescending
3) Could sound like I doubt the validity of their claim
4) Could sound accusatory
これはあなたの車でしょうか?
1) Used to ask a plain old question
2) Could be used to get confirmation
3) Could be used to express doubt
The point is that none of these are equivalents in terms of nuance and feeling, or even usage other than the fact that they modify the conveyed feeling and intent of questions.