Actually, "biannual" means twice a year. The part of the phrase the FAA dropped from the regulation, "biennial," means every two years, the story is, the FAA dropped "biennial" to encourage periodic recurrent training in GA, but I suspect the real reason was lack of English language competence.
(actually, a BFR wasn't really "biennial" to begin with.)
@Clip4 gave the answer to the real question. Unless there is a reason for the FAA to examine your logbook, chances are the question will probably never come up. Even then, it would be rare for the FAA to ask to see more than the entries that show you were current at the time of the event under investigation, not whether you were current some time in the past. If the investigation is that deep, the lack of the flight review is probably the least of your problems!
Get the flight review. Go forth and sun no more.