I found a big spider, 2 full inches long with bent furry legs, 4mm wide,
splayed evenly at roughly 45^ angles. All dark grey.

How can there be only one of them? I had never seen another spider
anything remotely like it in the house and it's been 2 weeks and I
haven't seen another one yet. (This one had an accident and he's dead.
A UPS fell on him.)