I had 3 beers 24 hours with out knowing that I had to take an EtG test the next day. Is there any chance that it can come up negative?

It is possible but not likely. Average elimination time would be in the range of 36-48 hours although the range could be as little as 16 or as long as 56 hours. Of course with EtG tests there is always the false negative factor and laboratory error.