I want to be able to convey sth, but cant’t seem to find the appropriate phrase to say it. Like say, sbdy comes up to you and asks a question, and you want to be able to say that you though you had the information and came in touch with it, you dont remember it offhand(and cant tell it immediately without referring anything), you would have to probably refer sth(tutorial,diary, ask someone) to tell the answer.

How to say it?

Could I say: I don’t have it on my (finger)tips? or I dont have it in the top of my mind? or I cant tell it offhand? or plainly: I can’t recall now?

Any suggestions?

Thanks