It's amazing how many people still believe in the microfracture death biner. I can't find the link now, but I recall reading about a study Black Diamond did. They collected a large number of biners at the foot of El Cap (or somewhere at Yosemite) that had been dropped hundreds of feet. Discarding the clearly broken ones, they subjected these biners to the kind of pull test that a brand-new biner would be tested in a QC sample. The dropped biners failed at the same strength rating as new biners.
If your dropped biner isn't obviously damaged and the gate functions normally, there's nothing wrong with it.