Ask HN: I've forgotten which social signup I used

Sites that use multiple social signup methods (Facebook, Twitter, LinkedIn, etc.) don't seem to have a way to check which method was used to sign up in the past.

Am I missing something? I'm surely not the only forgetful person.

Short of signing up with each method, I can't figure out a way to look up or reset account access. (I'm looking at BrandYourself.com, but this is relevant for every social signup enabled site I've come across).

Anyone have tips?