Is it common for a filshie clamp to be left inside a patient after a full hysterectomy (ovaries stayed). a clamp was removed during the procedure but 1 is still present?

That could be a technical issue so you should discuss with the GYN doctor who did the hysterectomy.

There is no harm that one clamp still remains. Since in the past a portion of the tubes were typically left with the ovaries it would have been quite easy to remove only one. The more recent standard has been to remove the tubes even when the ovaries are left as doing so may reduce the risk of ovarian cancer, in which case a clamp may have migrated or been hidden in scar tissue.