@jiministicc Dm him i guess?
Like go with,
Hey!(name) It's you right? Remember me?
If he does recognise u he'll answer otherwise he'll be like 'uhm? Who are u?"
Now you have 2 options
You can play along and be like, 'guess, not tellin ya' or you tell him who you are. I'm sure he'll recognise you cuz he already did last month!
If u decide to Tell him who u are then go like this,
'yk? (Name) your ex neighbour?'