I call bull on Douma actually remembering Inosuke based just on his face (unless there’s some specific incident to the backstory that made him remember it, like Inosuke’s mom hurting Douma or Inosuke having a very very very specific facial feature, etc).
But still, my parents friends who saw me with them when I was 5 couldn’t even recognize me again when I was 17 by myself. Douma’s on some adderall if he can remember Inosuke based on his adult face when last he saw pig pillar was probably as a baby (based on his recollection of his mother letting him go a few chapters ago).