Kinda superficial – to be ‘at’. It only says you were there: ‘at the station’, ‘at an exhibition’, ‘at a party’. All of them – just places. The relationship to place obfuscated. It’s the default preposition in our language.
So you were at the party. It could be one of those evenings in which you’re fully immersed. The mind and body all lost in opportunities and potentials and speculation. Or it’s somewhere where you just sat.
Actually it was neither. We were standing, in the backyard, though ‘at’ would be much more suitable because a default position was my position. I was lingering under a willow branch invited to this party by a friend. You said it was the same for you. The only thing we had in common was that we didn’t know anyone else.