I feel like I should be wearing a sign:
"Hi my name is [XXXXXX]. If I don't remember you, or the fact that we had that amazing time at [XXXX] or that we roomed together while I was studying at [XXXX] or that we once overthrew the government of [XXXX] while wearing [XXXXX] and drinking [XXXXXX], please don't be offended. My memory is a bit threadbare. I am just happy to see you, my dear [XXXXXX]."
"Hi my name is [XXXXXX]. If I don't remember you, or the fact that we had that amazing time at [XXXX] or that we roomed together while I was studying at [XXXX] or that we once overthrew the government of [XXXX] while wearing [XXXXX] and drinking [XXXXXX], please don't be offended. My memory is a bit threadbare. I am just happy to see you, my dear [XXXXXX]."