An/the armchair

Hi,

I'd just like to make sure about this. Let's say I meet someone I haven't seen for a year. I say:

"The last time I saw you, it was at a party and you had too much to drink. You were slumped in an armchair."

"The last time I saw you, it was at a party and you had too much to drink. You sat slumped in the armchair."

"An" or "the" armchair? I can use either here, right? I prefer "an" because for me "the" would be better if there was something distinctive about that armchair to emphasize it after a year. So I'd use "an" even if there was only one armchair in the room. But "the" can work too - the person who was drunk might remember which armchair I mean.

Does that make sense?