PGS Vanishing Twin

Hi! I transferred 1 PGS normal embryo. At my 6 week scan we saw 2 sacs, 1 was empty. The embryo split but didn’t develop. My doctor said it’s “extremely rare” for vanishing twins to be identical. But it happened to us! The surviving embryo had a strong heartbeat and was measuring correctly. I am worried about the effects and health of the surviving embryo. Has this happened to anyone? TIA!