Car was feeling funny after AX, like when you change lanes
it took more input to get it to straighten out again.

Felt left rear wheel, movement similar to when front bearings
are loose. Felt castle nut , no cotter
pin left. Jacked up, wheel moves 1/4" in vertical plane. Oops.
Maybe I used too small a cotter pin, but crap the thing was
just better than hand tight by this point.

Anyhoo, I air-wrenched it on good again, put in the biggest
cotter pin that could possibly fit, and feels good (in garage).

Question is, would driving like that have already ruined the
wheel bearing?

Thanks,

I had that happen. The rotor dragged against the pads and toasted the caliper seals. On top of that, the lateral torque applied to the bearing wallowed out the bore in the trailing arm, trashing it as well. If your bearing is shot, I would expect that it would communicate that to you in some way, if not thru sound then thru temperature. Compare one side with the other. I heard from a reliable source that trailing arms, nla for years, came back from Porsche at reasonable cost.

Does it wiggle after you tightened it? Yes then the bearing is shot. Little tiny wiggle is OK.
No wiggle you better go play the lotto cause you got lucky.

So far looks good. I'll probably put a new one in after
the season anyway.