I'm Looking for My Missing Shiny Alolan Sandshrew Now Probably
Evolved..!! I Give The Pokemon To My Friend.. But He Wonder Trade
Maybe Coz I Can't See Pokemon In His Storage Box
Your friend could have wonder traded it, auctioned it, released it,
or anything that would "remove" that Pokemon from their account. If
you don't see either Shiny Alolan Sandshrew or Sandslash then I'll
bet one of those things happened.
You're best bet would to ask them what happened, and if they
released it and you want it back to use the Pokemon
recovery tool.
If they sold it/Wonder traded it unfortunately there's really
nothing you can do.