And please feel free to tell me if I am freaking out over nothing ; ).

Looks like something bit a hole in the leaf, probably when it was small and growing and did the plant equivalent of severing an artery, so the whole part of the leaf fed by that tubule died. There are probably other opinions.

any recollection of a minor hail storm??

Agree with Kathy and I wouldn't worry about a single leaf. But you were right to remove and dispose of it.

Whew! Thanks all!

Yes - we definitely had a couple bouts of small hail during the spring (and may be getting some today). But I've also fallen behind in my slug deterrence this year, and between them and whatever other bugs and critters there may have been at work out there, I've got lots of little blemishes on the plants. I just have seen some photos of nematodes, and every time I see something that looks remotely like that I probably overreact.

Guess I should just take a deep breath....