NOT A TEACHER
In my opinion, the sentence cannot be paraphrased in that way:
1) We went to Budapest 2 days ago. (It means how many days ago someone [STRIKE]was[/STRIKE] went somewhere; a person might have stayed in Budapest more than a month or longer). They can't have stayed in Budapest for a month if they only went there 2 days ago.
2) We had been in Budapest for 2 days, before we got our return tickets. (exactly two days before something happened)
3) We have been in Budapest for 2 days. (It means that someone has been somewhere until now, but we do not know exactly when) Yes we do know when - 2 days ago. We also know who it was (We) and where they were (Budapest)
My version is as follows:
We were in Budapest two days ago.
or
We travelled to Budapest two days ago.