Could a short luteal phase cause a miscarriage at 11 weeks ?

Although possible: Most miscarriages are due to a chromosome abnormality in the embryo.

Luteal phase defect: Most luteal phase defects cause a loss earlier like 6-9 weeks. 11 week loses are usually related to things like subchorionic hemorrhage. Of course a luteal phase defect could cause a loss, which isn't picked up until 11 weeks. It may be of value to check a Progesterone level in the first trimester with subsequent pregnancies.