use tempdb;
go

create function dbo.fnColumnsInfo
(
  @name sysname
)
returns table
as
return (
 select
  c.name as column_name,
  pc.is_dropped,
  pc.leaf_offset
 from
  sys.system_internals_partition_columns pc join
  sys.partitions p on p.partition_id = pc.partition_id left join
  sys.columns c on column_id = pc.partition_column_id and c.object_id = p.object_id
 where
  p.object_id = object_id(@name)
);
go

create table dbo.t
(
 a int,
 b int
);

select * from dbo.fnColumnsInfo(N'dbo.t');
go

alter table dbo.t drop column a;
select * from dbo.fnColumnsInfo(N'dbo.t');
go

alter table dbo.t rebuild;
select * from dbo.fnColumnsInfo(N'dbo.t');
go

drop table dbo.t;
drop function dbo.fnColumnsInfo;
go