If there's not too many entries in the tables, it may be quicker/easier to loop the table items.
Code:
; /gethigh <Table> (/gethigh @Number.1)
alias gethigh {
  var %i = 1,%a = 0,%b
  while $hget($$1,%i).data {
    if $v1 > %a { var %a = $v1,%b = %i }
    inc %i
  }
  echo -a $1 $hget($1,%b).item == %a
}