precisely!
In all seriousness: the reason moose does not umlaut is that it was borrowed from Algonquian "moos" during the Modern English period, over a thousand years after the sound change that produced umlaut.
There have been pre-Old English sound changes that have been generalized to other words, but that's typically Indo European ablaut (e.g. sing -> sang -> sung) which has spread to verbs like sneak and dive.