I am enjoying this thread (and not just because most people seem to think it was more my DWs fault.. he he!)
Answering some of the questions comments ..
(NB: in the OP I deliberately switched roles. In fact it was I who went to the bar leaving my glasses where we were sitting, and my DW who then moved to grab a table, and left them behind. I know it was confusing but I suspected a tendency on MN to side with the female)
1 - I am surprised how many people's eyebrows were raised at the thought of my DW going to bar! I thought that what with, um, feminism and all, men and women were beyond all that stuff. We both go to the bar (unless perhaps it is crowded when experience shows men do get noticed and served quicker, in which case obviously I would always go) Gosh perhaps I am too liberated. Should I offer to go to the bar for female work colleagues?? Perhaps that's an AIBU in itself.
2 - glasses were in a bright yellow case so easy to see. No, I didn't say 'look after them for me' (my bad) but equally DW didn't look around else she would have seen them easily.
3 - I said 'ledge' I don't know how else to describe it - like a large kerb, along the edge of grass, and quite a few people (who hadn't got tables) sitting along it.
4 - I use my glasses for reading only. I had got them out to read something, and then put them down next to where we were sitting.
5 - don't worry we didn't argue about it for long! (about two days)