Well, this is very simple, if someone BIN wihtout fg, just report that post (or not) and ignore that BIN.
Just quote and said something like "invalid BIN since no fg, my bid is X" so is clear that you want to keep with the auction.
Most sellers will keep the auction open and sell it to a new BIN, if any, if the first one doesn't have the fg or to the highest bid if the auctions end, the only difference is that they may try to contact the the one who BIN first to get a bit extra FG but usually no ones waits to much for that.