My obgyn said i probably failed the 1 hour glucose screening due to fasting beforehand. could this have caused an elevated number even while fasting?

No, fasting does not cause higher sugar level with one hour test but this test is only a screening test. The purpose of one hour test without fasting is to rule out the population without gestational diabetes, i.e. if you are not fasting but your sugar level is not high after one hour you very likely do not have gestational diabetes. You should proceed with 3 hour test for confirmation. Good luck.