What is the ruling on saying "Ya Ummah" (Oh Mother) or "Ya Ummi" (Oh My Mother) when startled or afraid, and is that considered Shirk (polytheism)?

Not every call to an absent person or an inanimate object is polytheism (shirk); the ruling differs according to the intent of the call. In the Arabic language, a call (nida') can be used for various meanings that are understood from the context and indications. So, whoever calls upon other than Allah and does not intend to ask of them, but rather has a rhetorical, literary, or emotional purpose, has not committed seeking aid from other than Allah. It is a condition for prohibiting calling upon the dead, inanimate objects, and the absent that the call be literal, not figurative, and that what is sought and requested from the one called upon is something that none but Allah can accomplish. As for a figurative call, no one prohibits it.